Functional testing is what is usually misrecognized as “manual” testing or another “favourite” bullshit “term” > “exploratory” testing. This type of testing consists of you, as QAE, acting as a user, using the system as a user would, interacting, checking, exploring, doing whatever you wish to do. Sure, there are those who love to argue about meaningless (pointless/impractical) details like that Functional testing is actually testing the functionality and it is not necessarily related to “manual” testing. Suck dick. Things should be as simple as they can be but no more, and as complex as they need but no more. Inventing artificial separation is rarely helpful.
The goal of Functional testing is to ensure that the functionality provided by the system actually works, is functional (as opposed to dysfunctional). That activity is something that every, EVERY single QAE, “SDET”, “tester” & etc should do, every day, no exceptions and guess what? It’s something that everyone in the company should be doing at least twice a week. At least. Using the product by as many people as possible, as often as possible is what breeds and enables excellence.