Cloud Strife is a young 21 year old man who is now mercenary but was once amember of SOLDIER. He is a complicated person that many people still wonder exactly who he is. In the game, he starts out as a mercenary who can be hired for any job. However, that changes when he meets Tifa and joins AVALANCHE.
Cloud has a complicated story since his life was changed and altered all because of SOLDIER. At the beginning, he is not sure of his memories due to the effects of Jenova and the mako he is injected with. His life starts out normal before he leaves to become a SOLDIER. He doesn't make the ranks that is hoping for. However, he does end up helping his best friend, Zack, and defeating Sephiroth for the first time. The defeating of Sephiroth is the reason Cloud's memories are messed up and he has mako in his blood.
His memories do not return back to normal till he falls into the Lifestream with Tifa. There, Tifa repairs Cloud's memories allowing Cloud to become stronger and fight Sephiroth. His true strenght, however, comes from a young woman that was killed by Sephiroth, Aeris.
Two years later, though, events are a little different for the movie, Advent Children. Cloud is distant from everyone. He believes that he is unable to do anything such as protecting the people he cares and loves. He is also sick with a disease called geostigma. Througout the movie, Cloud tries everything to avoid, but in the end, he comes face to face with Sephiroth. It is at the ending that he realizes that he is home, that he does have people who care and love him.