I suppose considering the receiver as a "processing center" is probably a good description, but in some cases this is not so.
Probably for the average person with some sort of a home theater system the receiver is the brain of the system. It may also dramatically reduce the wiring clutter most of us deal with and have dealt with forever.
Todays receiver, using hdmi,component,etc, is the hub. The cable box/set top box will take the signal from the wall outlet and send it to the receiver. The DVD/CD/Blu-Ray/etc. player will send the signal to the receiver. Gaming systems will do the same.
The signals from each, and others not mentioned, device may or may not be "processed" in some fashion but rather input through the receiver and output directly to the tv. It depends on the device, how it is connected and what you want or don't want the receiver to do with that signal.
The ability of the receiver to control, process, etc. the signals is dependent on the features of the receiver.
The receiver may offer the capability to control all incoming/outgoing signals but you still have to manage how you want each device to be managed.
Today's receivers also offer, maybe well done or not so much depending on the quality of the receiver, some sort of audio calibration, equalization, room management for the audio signals. Depending on the quality of the system used by the receiver this can provide an improvement in sound for the system/speakers.
In general while the receiver is a "hub" you still have to control how the signals are input/output and processed for each device by the receiver by how you set up the receiver, how the devices are connected and what you want the receiver to do. The remote is the key here and understanding how the receiver handles/converts/passes through/etc. all the signals requires knowledge of the system. It's not hard but does require reading and practice for a bit. Like all things the more you practice/use something the better you get.
