What are the "Rain-sensing washer-linked variable intermittent windshield wipers" and how do they work?

I do but I don't know how to use them yet, My husband does.
There is just so much stuff to learn. I still enjoy driving My 97 Avalon......Gotten use to every thing on it. *-*

we have a 2011 Avalon Limited with rain sensing wipers and sometimes they work and sometimes they don't. We have no problem with them on our 2007 RX350 though.