A blind man walks into a bar...

A blind man walks into a bar.
And a table.
And a chair.

This is a bar joke, and it is also a slapstick joke. This joke also makes fun of people with disabilities. The humor in this joke comes from the fact that the setup makes you think that the blind man is walking into a place that sells alcohol, and that the joke will happen inside such a place.

In fact the setup says that the blind person is just walking into things because he is unable to see them. Often people getting hurt is considered to be humorous in western society.