The EX bar is used to do EX moves and Super moves. EX moves are performed the same way as normal special moves, but you press two punches or two kicks instead of just one. They have improved properties like more damage, faster speed, or invincibility. If you have a full meter you can do a super move, which does a bunch of damage but uses up the entire thing. Most of the characters can combo into their supers, but generally speaking its usually a more efficient use of your EX meter to use it on EX special moves.
The meter below the life bar is a stun meter. As you hit enemies, it fills up. If it fills up all the way they are stunned, which lets you get in a free hit (so you should use that opportunity to do the most damage you can). The meter will go down if you go a second or two without attacking them, though, so keep the pressure on when you've built it up.
