Let's see the differences:

• A functional test aims to test a specific feature; however, a regression test aims to ensure that the previously tested features continue to work.
• A Functional test is conducted during the development phase but a regression test is conducted after bug fixes, updates, or code changes.
• In a functional test, our focus is on the new function. In a regression test, our focus is on the existing(previous) functions.

For example, we test the login page in sprint 1; this is called the functional test. In sprint 2, the backend guys update some APIs or authentication logic in the login flow. Here we should retest the login flow; this is called the regression test.