A charge character is a character whose move set is based around charge moves. Some characters are debatable as to whether fit this description, but lots of them are pretty clear.
Charge characters can be a bit tough for beginners, owing to the timing requirements of the commands, but many charge characters have great move balance, so more experienced players can use them pretty easily.
Because charge characters do not excel in combo games and games with preemptive blocking, they have not been too prevalent in recent games.