What is the deal with the new Toyota Prius hybrid that you can plug in?

I saw it advertised on the Toyota website. I actually went to the the Toyota dealership today to look at a totally different car, but I asked about this new upcoming Prius to find out how exactly it worked. The salesperson started to say something that made no sense, and then sort of backed up and admitted she knew nothing about it really, only that it was coming out next year.

So it is plug in, and gas, and a battery? Logically I guess that means you can charge the battery with electricity, and if it runs low on charge it can use gas, so it solves the problem of long distance driving for electric cars? But, I am just guessing.

What have you heard about it?

What do you think?