We put a bird (satellite) in a high (stationary or geosynchronous) orbit. The bird is so far from the earth that its orbital speed matches the rotational speed of the earth. It's moving, and make no mistake about that, but at the same speed the earth turns. We point a microwave antenna (a "dish") at it here on earth, and take whatever information (TV signals, voice and data information, top hush military stuff) and transmit it up on our uplink. We're in business.
Up in space, the receiving antenna system captures the incoming signals and routes them through an amplifier network. It then retransmits those signals at whatever frequency is appropriate for what is needed to get the signal to the targeted receivers. It might be a very narrow spectrum of microwave frequencies with a number of "channels" like is used to transmit programming to cable television company receiving stations. These downlink receivers are usually at the "head end" of cable distribution system so the signals can be "separated" and put down the cable as different channels. Or it might be a high power transmitter like DISH TV or DIRECTV where each channel on the system is rebroadcast and a dish anywhere in the coverage area can "hear" all the signals. (We just need to pick a channel.)
In the case of telecommunications, a band of frequencies is set aside, and the voice and data (in digital form) are uplinked and then downlinked to appropriate receivers. If you're talking on the phone or using the internet, some of your data packets could be routed through a satellite, depending on who you're talking to and what you're doing on the world wide web. Voice and data communications and the web are "merging" in some ways through the use of satellite communications. They're all just data streams anymore, and the current systems just handle digital signals; they don't care whether the data stream "came from" analog voice or sound signals, image or video signals, or anything else.
The satellite could be looked at in some ways as a sophisticated "reflector" of ground-based signals. We beam 'em up, and then the bird sends them back at us. Certainly there is a lot of high tech stuff at work here, and more specific information can be gathered by doing a quick search of WikiAnswers. Or you could ask another question. A link is provided below for more detail. It's to the Wikipedia article on the satellite itself, and by reading this, you'll be able to "see through" the system to understand how it works.