Slaves were people who had originally been captured in foreign wars, or were born into a family of slaves. Slaves could be bought or sold like goods and were used to do hard work or help out in the home or on farms. Slaves were also trained and used as gladiators in fights in the amphitheatres.
Greek slaves were especially valued, as they were well educated and could be used to teach. Many slaves were treated well, and sometimes they would be granted their freedom, and even then, they might continue to work for the same master.