What is the meaning of "back burner"?

The usual expression is "put something on the back burner". Most gas stoves in our country have two burners. In the U.S., most stoves have four burners — two in the front, and two in the back. I understand dishes are normally put on the back burner when they don't require the cook's immediate attention. So, when you say that you are putting something on the back burner, what you mean is that you are postponing doing it. You are putting the work aside because it doesn't require your immediate attention. Here are a few examples.

*Right now I am busy getting the plans for the house ready. I am afraid I'll have to put my tennis lessons on the back burner.

*Rohini has decided to put everything on the back burner till the end of the semester.

*Bush's plans for invading Syria have been put on the back burner.