How is stand your ground different from self defense?

This topic has been brought up a lot on the news but it still confuses me.

For an example , I'm in my home and a burglar breaks in .
As far as I know in every state you are legally allowed to use deadly force.

If I'm walking down the street and I'm assaulted by a person or group of people
I am legally allowed to use deadly force to protect my life.

How is stand your ground any different than self defense?