Duelist:
One-handed melee weapons deal +2 damage. Two-weapon fighting adds your attribute bonus to damage. If you have a hand not holding a weapon, you gain +1 AC.
Great Weapon Fighting:
When using a melee weapon held in two hands, odd rolls on weapon damage dice are maximized. So a 1 on either of 2d6 from a greatsword becomes a 6.
Archer:
You gain a +2 to hit with ranged weapon attacks. If you haven't moved since tgmhe start of your last turn, you can make a ranged weapon attack as a bonus action: this reduces your movement speed to 0.
Brawler:
Your unarmed attacks deal 1d6 plus your strength modifier damage, or 1d8 if both hands are free. So long as you have a hand free, you can push or grab as a bonus action.
Defender:
Your AC is increased by 1. You can replace your dex bonus with your str bonus to AC calculations if you are using a shield. When a creature within your reach, or who you are offering cover to from the source, takes damage, you can reduce that damage by 1d10+your strength modifier as a reaction.
Skirmisher:
Your ranged attacks do not suffer disadvantage from being adjacent to an enemy. If you weapon attack an adjacent creature you did not start the turn adjacent to, you deal an extra +1d6 damage. Creatures you have damaged cannot make opportunity attacks on you on the same turn.
...
They are designed to overlap slightly, offer a range of options within them, and give a different style of play for each one.
For example, Duelist and GWF both boost a versatile weapon, and you get +1 AC by holding it in one hand off your turn.
Or duelist and brawler with a hand free.
Defender stacks with most styles.
Skirmisher works well with duelist (more taps) if you go twf style.
Various double weapon feats (pam, double scimitar) work with gwf.
Archer with throwing weapons works with duelist. But archer/skirmisher is also tempting.
