Feats

Feats either add a special skill, or improve an existing one, allowing your character to do things that are usually considered not possible without the feat. For example, drawing a weapon so fast that it doesn't give the opponent time to react, being able to use a specific combat move particularly well, or bypass a restriction that would apply otherwise.

Some feats have pre-requisites (which can be ability scores, skill ranks, or already having other specific feats) before they can be gained. It might be smart to plan what feats you will want at some point in the future, so you can pick up the pre-requisites along the way.

You get one feat at character level 1, and a new feat at lvl 3 and every 3 character levels afterwards, regardless of what your class levels are.

Humans get an additional feat at level 1.

Fighters get an extra feat at lvl 2, and then one at every even-numbered level (4, 6, etc.). That's in addition to getting a feat every 3 character levels (and another at level 1 if they are human). Lucky overpowered bastards.

In the PHB pdf: Check out pages 91-92 for the feats list and 90-103 for detailed descriptions.