The Pilot:
Charles Xavier is Profesor of Xavier institute.He is a mutant.He was the close friend to Erik Lensher aka Magneto.He was the mutant too.Erik brutally punch Charles with one spear from old museum in the legs and Charles would never walk again.Erik then becomes Magneto the master of Magnetism.Charles was codenamed Profesor X.
He founded a team of mutants to serve to him.They are Scott Summers aka Cyclops,Jean Grey,Henry McCoy aka Beast and Warren Worghtington III aka Angel.
Magneto found a team of villains.They are Raven Darkholme aka Mystique,Cain Marko aka Juggernaut and Motimer Tonybee aka Toad.
They attack Xavier Institute and then becomes beaten by Charles team who are later codenamed X-men.
The X-men:
Profesor X founding a new mutants.Logan aka Wolverine and Ororo Monroue aka Storm.Storm had a love with Beast.Xavier Institute attacks one mutant that called Sabretooth.He was tracking Wolverine.Wolverine knows him as his half-brother but he lost recollections.
Sabretooth beats Wolverine and get him to Canada.X-men Charles team tracking Sabretooth and find Wolverine.They are together beat Sabretooth.Logan wake up in Xavier institute.
Later in Canada goes Magneto with his Brotherhood team and find Sabretooth.Sabretooth becomes a part of Erik's team.