In Software Development Life Cycle QA testing is one of the fundamental steps to build a quality product.
Different aspects of the Software is tested via different tests which can be divided into 1) Functional testing
2) Non functional testing

• Functional Testing 1) Functional testing specifies that the operation of a program or mobile application performs according to business requirements. 2) Functional testing are usually performed manually and before non-functional tests. 3) The tester provides the specific input to the program and compares its result with the expected output. Functional testers don't care about source code, they only focus on checking the functionality. 4) Functional testing is necessary to ensure that the product is free of any bugs or vulnerabilities.

-Non-Functional Testing
1) Non-functional testing covers all the aspects not covered by functional testing. It covers the performance, availability, scalability and reliability of the software.
2) It is performed to ensure that interests of the end user is fulfilled. It makes sure the Product/software doesn't fail in the market/customer place. It increases the market value of the product.
3) If functional tests specify what program you should do whereas non-functional tests describe how it should behave.
4) Non-functional tests are usually automated. Dedicated tools help model-real world environments to check how the software behaves under various preset conditions.

• Functional vs Non-Functional tests

  Functional Tests Non-Functional Tests
  
  1) Tests Features/Functions 1) Tests Non-functional
  aspects

2) Evaluated as either present 2) Evaluated on the

or not present scale

3) Usually done manually 3) Usually automated

4) Checks the accordance to 4) Checks the
customer requirements accordance to end
user expectations
5) Tests what product does 5) Tests how product
does
6) Requirements are easy to 6) Requirements are
specify hard to specify

• Functional Testing Example An online portal on which user logs in with their user account and password. The login page has two test fields for username and password. It has two functions - Login and Cancel

When successful login it goes to Home page and cancel button cancels the login.

• Non-functional testing Example Upto 10000 users login at the same time and the application load time should not be more than 5 seconds.