why did slavery (during the civil war) happen?

what is the significance or importance of the event?

Southern farmers bought slaves to perform labor on their farms and plantations. They believed that slaves were cheaper than paying wages to free men.

The significance is that slavery divided the country. It had a long lasting effect even after the Civil War as discrimination and prejudice against African-Americans continued for generations and hasn't been completely eliminated even today. Slavery dehumanized both the slaves and their masters.