Validations confirms Have we built the right software

It is the process of evaluating a system or a module during or after the development process to find out whether it satisfies the requirement or not

It is done at the end of the development process and takes place after verification are completed.

Validation is done at different levels in different ways such as
1. Unit Testing
2. Integration Testing
3. System Testing
4. User Acceptance testing

Unit Testing :-

It a testing of a very small unit of a software or a piece of a code generally it is done by the developers.

Integration Testing :-

when some small modules are integrated together then integration testing tests the functionalities as well as data flow in between the two modules.

System testing :-

It is a testing don after the whole system is build or we can say that in system testing we do test the system as a whole.

User Acceptance testing (UAT) :-

Before the product or an application is deployed to the client or before client starts using it, it is tested once.
Alpha testing :- Testing done by the software firm at their own location.
Beta Testing :- Testing done by the client on their own location.