Yeah, basically its a way to spread data over multiple drives...
Raid 0 (Stripe) - Lets you make multiple hard drives into 1 large one
Raid 1 (Mirror) - Lets you write the same data to multiple hard drives. This way if one drive fails, you can still get the data on the other drives.
Raid 5 - This allows you to use 3 or more drives, and again create one large drives, or multiple smaller ones. When using Raid 5, if a drive fails, you can replace it with a good drive, and then rebuild the data onto the new drive.