What are “Black Codes” practiced in the South after the Civil War?

After the defeat, white Southerners blamed blacks for the war. Black officials were elected, and where they were, they raised taxes for schools for black children. Whites bitterly resented this.
There was a completely paranoid fear that blacks would take over the whole South and that they would take everyone's property and rape all the white women and never do any work and make everyone broke. Vicious racism fed the widespread terrorism of not only the KKK but also of white gangs everywhere.
Once blacks were too afraid to go to the polls, whites passed all kinds of laws to keep them from voting. Penalties for blacks were much harsher than for whites - the theft of a chicken by a white person was a misdemeanor, but for a black it was a felony with a five year sentence. It was illegal for blacks to travel at night, because of course they were always plotting criminal mischief. The economic system kept most blacks tied to the land through the share cropping system, which paid so little it was very hard to break out of it. Segregation laws denied blacks access to decent housing, hospitals, schools, and on and on.
In my arrogant opinion the government should have hung 100,000 whites after the war, and I'm white.

Wikipedia has a great article on this and the Jim Crow laws.
You should really bop over there.

State and local segregation laws

Go to google.com. Type in "black codes." There ya go.