A receiver is that big, heavy thing that you plug your speakers and other components into (like a DVD player, TV, CD player, Xbox, PlayStation, iPod, and etc.). It's the "brain" of the show, really. The idea of connecting all your components to a receiver is the concept of audio/video switching, allowing you to switch to different video sources (like TV, DVD, camcorder) on your TV and thus changing the audio source accordingly - all without touching anything but the receiver.
It's the "brain" of the show, really.
Of course, the main purpose behind audio/video switching with a receiver is to drive audio to external speakers, like surround sound or stereo speakers.
Most receivers have a plethora of inputs; up to 8 speakers and a subwoofer (more commonly, 5.1, or five speakers and a subwoofer), several video inputs, and even HDMI inputs. You could plug your Xbox, Plasma, and DVD player into the receiver and use one remote to switch between all the different video sources (games, TV, DVD video) and have your speakers pump out surround-sound. Let's start with inputs and outputs. If you don't understand something, read through the entire How-To as most of it will be explained in detail.
Keep in mind that a receiver is the hub of your entire home theatre, so this How-To will actually guide you through the basics of connecting your complete home theater.