Question about retainers

[Tsunami]

What do they do exactly? I know that they keep the teeth from shifting after treatments, but isn't that the job of the braces, to keep the teeth in place while the roots transition themselves properly?

Sorry for my ignorance.

[statisticschick]

Tsunami,
I stopped wearing my retainers about two years ago. Within a year, my teeth had significantly shifted. And I'm 28 years old!!! I'm going to an orthodontist tomorrow for a consult. I am hoping that I can correct the problem by immediately starting to wear retainers again.