Satellites are tournaments where the top finishers get prizes in the form of tickets to other tournaments that have more expensive buy-ins.
Regular tournaments that pay money have rapidly increasing pay jumps as you get closer to first place, however for satellites you're playing to place in the top finishers. For example, if the top 5 players all get tickets, then the tournament ends when there are 5 players left rather than playing until only one person has all the chips. This has a huge impact on the strategy of play as you get close to the bubble.
The benefit of a satellite is that you can get into a much more expensive tournament than you can afford, the drawback is that unless you understand the differences in strategy between satellites and regular buy-in tournaments you're probably going to be just spinning your wheels.