Sky, hehe

Foreshadowing....kinda...not. :P

What's a feat?

About 30 cm, give or take.

Amazing joke, but to actually answer the question, a feat represents a special ability or specialization your character gains. For example, feats could:
•make you better at a particular task (e.g. attacking, disarming, or reacting faster during combat)
•grant you a new skill (e.g. the ability to craft certain items, take an extra attack action per turn, or use a piece of equipment with which you were previously unskilled)
•change how certain actions work (e.g. making your spells behave differently, using your dexterity bonus instead of strength bonus for melee attacks, or increasing/decreasing the distance your attacks can reach).

This is only scratching the surface, 3.5 had a ton of feats that do all sorts of different things. Here's a link to the original Players Handbook 1 list of feats for more details.

https://www.d20srd.org/srd/feats.htm