what is requirement?

Customers or Clients requirements with respect to software are known as requirement.
There are two type of requirement-
(1) Functional requirement
performing operation on the application and validating known as functional requirement.

ex: open gmail.com login home page
enter the valid email id and password
(2)Non Functional requirement
validating the application layout known as non functional requirement.
ex:
application page overlapping
application page color
checking spelling etc.