What does the idiom get your drift mean?

"I get your drift" means "I see where your argument is headed, I understand the point you are trying to make." For example:

-Here's the Highway

-Let's stop and get some gas

-Why? I think we're all right

-Well, you know, it's kinda far, and there's lots and lots of nothing there...

-I get your drift. Better safe than sorry.