In the game he starts out as a cold, uncaring person, he doesn't care about anyone but himself:

"Shut up! I don't care about either Shinra or Soldier!

But don't get me wrong!

 I don't care about Avalanche or the Planet for that matter!"

But Cloud soon changes after he meets Aeris.

What did Aeris show Cloud?

Aeris showed Cloud that there are things worth fighting for, and just how important things are, that things have a meaning. Aerith showed Cloud hope, and gave him courage.

Cloud was very mixed up for half the game. He didn't know who he was, his memories were all screwed, but then Tifa helped him find his true self again.