Douglass is born a slave and spends his childhood discovering what it is to be a slave. At first, he only sees terrible things happen to others, like his Aunt Hester.
As Douglass gets older, he starts to actually experience the suffering of slavery himself. But being punished and whipped regularly only makes him more rebellious. So his master sends him to Mr. Covey, a well-known "slave breaker," to be beaten into submission. For the first six months, this works.
After six months of punishment, Douglass decides that he would rather die than be whipped again. This resolve helps him escape to freedom. Once he's free in the North, he joins the Abolitionist movement to end slavery.