Ok, well all it is, is a fighting game, staring some of the greatest ever nintendo characters. These 25 characters are:
Mario
Dr. Mario
Luigi
Yoshi
Princess Peach
Bowser
Donkey Kong
Captain Falcon
Link
Young Link
Zelda
Ganondorf
Pikachu
Pichu
Jigglypuff
Mewtwo
Kirby
Fox
Falco
The Ice Climbers
Ness
Samus Aran
Marth
Roy
Mr Game & Watch
I don't know which ones you've heard of and which you haven't though.
My favourite character is Marth. If you don't know, he's a swordsman from Fire Emblem: