Why is a plane able to fly?

Because of what is known as the Burnoulli Effect. That is:
The higher the velocity of a fluid the lower the pressure.
Because the upper part of the wing has more curvature than the bottom of the wing, The air crossing the top has a longer distnce to travel than the bottom of the wing so the air on top speeds up to make up for the longer distance it has to travel,so it has a lower pressure. The higher air pressure under the wing pushes the plane up. The plane must be moving through the air for this to happen. Same principal in a wind tunnel, just that the air is moved and the plane is static.

Burnoulli may be spelled wrong, but I'll let you look it up
in Aerodynamics.

Many people have this queer misconception that airplanes flying could be explained by the Bernoulli's principle, this is only true for paper airplanes, real airplanes are too heavy.

Aeroplanes flying could be explained using Sir Newton's action and reaction pair effect. The airplane pushes down on the air beneath it and the air consequently pushes back up, with but a minute bit of help from Mr. Bernoulli.

because it has two wings like birds who flies and it has many carecteristics which help it to fly

to understand how a plane flies you need to understand the four forces that act on a plane. these forces are thrust, weight, drag, and lift. it is easy to understand the force of weight. it is basically how gravity acts on the plane. thrust is created when the propeller (it is designed the same way as the wings of an aircraft you will understand when i explain the force of lift). it is also created by the turbine in larger aircraft. lift is created when air passing over the wing has a lower pressure than the air flowing underneath the wing. the longer the wing the more lift is generated. that's why you hear of some planes being able to go to heights of 100,000 feet. if you look at the tail section you will see that the vertical and horizontal stabilizers are basically a smaller wing. drag is the friction caused by air particles bumping or rubbing against the wings. the faster you go the more drag you create. thats a basic rundown of the four forces that act on a plane.

Now onto what the pilot can do to manipulate how the airplane flies. the pilot can make the airplane bank, pitch up, pitch down, and turn. he can also manipulate the wings in order to takeoff and land. to pitch up or down the pilot will push or pull on what is called the yoke or joystick (a yoke is sort of like a steering wheel) to bank the pilot will rotate the yoke or push the joystick to the left ro right depending on which way he plans to turn which is the next thing i will explain. when a pilot wants to turn he will bank the plane and push on the rudder pedals to keep the plane coordinated.
i will modify my answer as soon as i can to help you understand how an airplane flies. i am going to have to do some research. there are many things to explain. i promise

http://travel.howstuffworks.com/airplane8.htm

Airplane Parts
Aerodynamics
Propulsion

Airplane Parts
A typical jetliner has wings, a fuselage, and an empennage with horizontal and vertical stabilizers. As the name suggests, these tail stabilizers act like the feathers of an arrow to make sure the airplane flies straight. Moveable surfaces on the tails are used to rotate the airplane nose up and down or yaw left and right.
Pitch
To maneuver, a jetliner uses control surfaces attached to its wings and tail. Moving the elevators up or down makes the jet's nose rise or drop (pitch axis).

Yaw
Moving the rudder side to side swings the nose left or right (yaw axis).

Roll
Using the ailerons banks the airplane left or right around it's roll axis.

Flaps and Slats
Jetliner wings have leading and trailing edge devices (slats and flaps) that extend during takeoffs and landings (low speed flight) and retract for cruise (high speed flight). The landing gear also retracts in flight to reduce drag. Jets also have swept wings. Wing sweep lets them fly closer to the speed of sound than airplanes with straight wings.

Spoilers
Jets fly so efficiently, in fact, that they need spoilers to help them slow down and lose altitude. Spoilers are hydraulically actuated panels on the tops of the wings. Pilots sometimes call them "speed brakes" or "lift dumpers," reflecting their function. On landing, they deploy even higher to make sure the airplane stays on the ground.


Aerodynamic Lift
Four forces come into play during a jetliner flight:

Lift — The upward force generated by the wings.
Gravity — The downward force opposing lift
Thrust — The forward force produced by the engines
Drag — The rearward pull as air resistance seeks to slow the airplane down

Wings
An airplane wing has a distinctive shape called an airfoil. Seen from the side, an airfoil is curved on top and relatively flat on the bottom.

As a wing moves through the air, it splits the airflow. Some of the air passes above the wing and some below. But because the wing's upper surface is curved, the air rushing over the top is forced to speed up.

The result is decreased air pressure above the wing. In contrast, the air flowing below the wing is slower and its pressure is higher.

The wing is lifted because the air pressure on the top of the wing is lower than the air pressure on the bottom. The faster the airplane flies forward, the more of this aerodynamic "lift" it creates. Flight occurs when the force of lift exceeds the weight of the airplane.

Note:
Aerodynamic lift is based on the Bernoulli principle, which states that the pressure of a flowing fluid decreases as its velocity increases. Daniel Bernoulli
(1700-1782) was the first person to define the fundamental relationship between pressure, density and velocity in fluid flows.


Glide
Finally, jetliners are highly efficient gliders. Even without engine thrust, they can glide about 20 feet forward for each 1 foot of altitude they lose. If all engine power were lost at cruise altitude, a typical jet could glide more than 100 miles (160 kilometers) before landing at sea level.


Propulsion
A jet engine uses a fan on the front to suck in air, mixes it with burning fuel, and blasts the expanded air-gas mixture out the back. In the process, it turns a turbine in the back of the engine that spins the fan in the front. Because every action has an equal and opposite reaction, a jetliner surges forward as its engines push air backward.

Fanjets
High-bypass-ratio fanjets are the most reliable engines ever developed. Fundamentally simple, fanjets are fuel efficient and quiet turbine engines. They feature continuous combustion and smooth rotation, unlike the internal-combustion engine of a car, truck or bus. A fanjet engine has three sections:

Fan unit and compressor section

Combustion chamber
Turbine section
The compressors pressurize air and feed it aft. Most goes around the engine core through a nozzle-shaped chamber. The rest goes through the engine core where it mixes with fuel and ignites. The hot expanding combustion efflux passes through the turbine section, spinning the turbine as it exits the engine.

The spinning turbine turns the engine shaft. The rotating shaft spins the fan on the front of the engine. The fan compresses more air and keeps this continuous cycle going.

a planes wing are an airfoil. the top of the wing has a longer distance for the air to travel. when the air is split up from top and bottom the air on top accelerates to catch up to the air on the bottom. this causes a low pressure atop the wing and the plane is "sucked" into the air. on the otherhand, fighter jets are more unstable and fly due to the shear power of there engines .

As the shape of the wings of plane is like an airfoil. When the plane is travelling, the wind will create a uplift force such that the plane is able to fly. By moving the flaps of the wings, the pilot can actually adjust the uplift and downward force which corresponding to taking off and landing of the plane.

I can't recall what they call the structure, but a wing is humped on the top. Therefore if you pass air quickly from the front to the back, the air will have to move more quickly as it passes the top. This creates a lower pressure, and that creates lift.