Slavery in antiquity was a practice that happened a long time ago and it meant that some people were thought of as property. People would own slaves, like they would own a cow or a horse, and those slaves would have to do all sorts of work for their masters (like cooking, cleaning, etc). In some cases, slaves were even traded like goods, just like food or clothes. It wasn't fair because the people enslaved didn't get to choose what they did and couldn't leave. They were treated very badly, which isn't fair or nice.