Please make your question clearer.
If you mean what does it do- Buffs your damage with no weapons or unarmed weapons (ballistic fist, power fist,zap glove, boxing gloves...)
At 50 and 75 skill points you get the ability to do uppercuts and crosses in and out of VATS.
Only one unarmed dialouge check exists, with one of Caesar's praetorian guards, with a check of 40, you can learn the legion assault, an upgrade to the forward+strong attack.
Veronica is the only companion who is good at unarmed (power fist).
If you tag unarmed, but don't tag melee at the beginning, Mitchell will give you his old boxing gloves.
Hope this helped.