Simple Circuit Request

I'm an absolute beginner at the electroncis groups, so forgive me if this is the wrong group.

I need to control an 120 VAC circuit with a PC. I'd like it to plug into a USB or serial port, and the circuit will be opened or closed based upon a control program running on the PC.

I think this is a simple request. However, when I googled for it, it came up with so many hits that I didn't know where to begin. Neither did I know how to refine the search.

So, I guess what I'm actually asking for is either a product, or search terms.

Thanks.