In a nutshell: He was a roman soldier that was enslaved. Later he was turned gladiator. During the gladiator rebellion he escaped with 10,000s gladiators and slaves (men, women and childeren). While he was escaped the roman army came after him up to 7 times, but he managed to defend himself and his friends due to superior tactics. It was only after the 8th time he was caught, but they didn't know for sure who he really was, so they decided to kill everyone just to make sure they had the right person. They never knew his real name, they only knew he was fighting like a spartan. Spartacus is a literal translation of the word spartan.
Any other questions?