Sub panels are actually called "remote distribution panels" and are a great way to deliver power throughout a building without having to run each individual circuit wire through the house. Instead, you run a larger amperage wire from the main panel (usually 60 amps or more) to a sub panel in another area of the home and then you can add the branch wires to that and they are closer to where they need to be.
When you have a sub panel, be sure to make sure it is wired properly. The main wire entering the sub panel should be "4-wire", which means it has 2 hots, a neutral, and a ground wire (like the one in the picture above.
When you have a sub panel, be sure to make sure it is wired properly. The main wire entering the sub panel should be "4-wire", which means it has 2 hots, a neutral, and a ground wire (like the one in the picture above.