Difference of functional testing and non-functional testing.

1) Functional testing :-
* it simple words, what is the system actually does is functional testing.
* to ensure that the product meets customer requirements and doesn't have major bugs.
* to verify accuracy of the software against expected output.
* it is performed before non-functional testing.
Example:-
* verify the login functionality (whether check the login user id and password working correctly or not)

2) Non-functional testing:-
* How well the system performs non-functional testing.
* to ensure that the product stands up for customer expectations.
* to verify the behaviour of the software at various load conditions.
* it is performed after functional testing
Example:-
*same login functionality, how secured the login functionality and how much time take user to get login page