Conditional Tense

The WEB site provided by respondent 002 explains the conditionals very clearly.

I would like to add a little explanation by addressing the questions directly.

What is conditional tense?
The "conditional tense" refers to the special use of the tense of the verb in a sentence using "if", to indicate a "supposed" scenario. It is more commonly called the "conditionals", which comes in 4 types.
conditional (0): general truth and scientific events.
conditional (1): real condition, possible present or future events.
conditional (2): unreal condition, present or future imaginary event.
conditional (3): unreal condition, past imaginary event.

How do we use it?
(1) use type "0" for condition which is possible to happen, and when it does, always produces a specific result.
e.g. If you heat water to 100 degree celcius, it boils.
(2) use type "1" for condition which can be fulfilled , and can produce present or future possibilities.
e.g. If we go to the market tomorrow, we'll buy oranges.
(3) use type "2" for condition which is not real, but if it is real, would produce a present or future imaginary event.
e.g. If I were you, I would accept that generous gift.
(4) use type "3" for conditions which was not real, but if it was real, would have produced the imaginary event.
e.g. If I had been you, I would have accepted that generous gift.

What do we have to notice when we use it?
(1) for type(0) conditionals, use "simple present tense" for both the condition and the event.
(2) for type(1) conditionals, use "present tense" for the condition. For events, use "present tense" for a "present event", use "future tense" for a "future event" .
(3) for type(2) conditionals, use "past tense" for the condition. Use "conditional" i;e. "would" for the present or future event.
(4) for type(3) conditionals, use "past perfect tense" for the condition. Use "perfect conditional" i.e. "would have" for the event.

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