some question about trainers

Hi ))
i dont was used any trainer, i leveled my profile to lvl 16 without nothing )

with what are trainers betters ?

can some one explain me ?

can i be banned for it ?

sorry for questions and my english ;)

trainer is better for faster leveling up
for example pursuit loader+macro gamer and you can go sleep watch tv or other activities
and you can be banned because is ilegal software