Tifa is the 20 year old bar waitress at Sector 7's 7th Heaven.  She takes care of Marlene along with Barret.  As an original member of Avalanche, she is a lethal weapon in combat, unleashing her fists as deadly weapons.

Limit Breaks
A note on Tifa's Limit Breaks, the more limit breaks you receive, the more damage you can do.  Okay, that was worded very badly, but if you have both of her Lv. 1 Limit Breaks, then a slot will appear and by luck, you may get Hit, Yeah!, or Miss.  If both of them are either Hit or Yeah, then Tifa will unleash BOTH limit breaks, doing huge damage, because it adds up.  And when you move on higher level limit breaks, then she unleashes ALL of them.
Lv.1: Beat Rush-Tifa lunges forward and punches the enemy a few times, doing damage.
Somersault-Tifa does a somersault kick at the enemy, doing slightly more damage.

Lv.2: Waterkick-Tifa does a sweeping kick that damages all enemies.
Meteodrive-Tifa picks up the enemy and drops them on the ground, dealing damage.

Lv.3: Dolphin Blow-TIfa appears out of nowhere underwater and smashes against the enemy with a dolphin, doing huge damage.
Meteor Strike-Similar to Meteodrive, except Tifa picks up the enemy, throws them up into the air, and slams them back.

Lv.4: Final Heaven-Tifa summons power from the sky to blast the enemy.  To receive Final Heaven, you have to play a certain tune on Tifa's piano in her house numerous times to receive the limit break.  The sequence is this:

Victory Dance
Tifa stretches out her arms and brings them to her back.