what is a orbital?

Definition of an orbital/subshell:
The volume of space, determined from wave mechanics calculations, where there is a high probability (over 95%) of finiding a particular electron is called an orbital. Each orbital can accommodate no more than 2 electrons.

Electrons can occupy 4 types of orbitals.
These are called s, p, d and f orbitals.
Theseorbitals are taken to be those within which there is a 95%of finiding a particular electron. Since an electron has a negative charge, its orbital can be regarded as a spread of charge. This is often called a charged cloud.

s orbital stands for spherical. Its shape is spherical.
p orbital stands for principal. Its shape is a dumb-bell.
d orbitals stands for diffuse. Its shape is a double dumb-bell.
f orbitals stands for fundamental. Its shape is undetermined.