Validation, This focuses on actual use of software/product or we can say testing the product according to the requirement specification.
*Functionality jaisi document m mention h software aise hi kaam kar raha h ya nahi. *
Basically Validation focuses on test execution part or we can say testing the software/application behaviour with respect to requirement. Or this is also called as dynamic testing

Where as Validation is done in any phase like Unit, Integration, System to check that it’s actually a mobile phone, you would be developing a beautiful mobile phone which cannot be used for basic call feature, so Validation comes into picture which talks from the Product’s final usage point of view. ask yourself are we building the Right Product ? as per the customer expectation ?

In industry it’s very easy to crossover Verification and Validation, in many places verification is not needed, only validation at higher level is enough, in some places verification is required at very lower level, to have a documentary evidence that each of the said requirement has been implemented well enough.

So that’s a simple understanding of Verification & Validation.
One more example to quote is from Healthcare perspective, you are developing a Blood Pressure measuring machine, how you are developing each functionality is checked by verifying each and every requirement implementation, and whether this is actually checking Blood Pressure in the right fashion as required is done using Validation, may be by Clinical Experts, Doctors etc. and both are done during entire Development Cycle.