What is the difference between The DCCC and The DNC?

Ok...so i'm a telemarketer haha. & right now my particular campaign is the Democratic Congressional Campaign Committee. It seems when I make my calls though.. a lot of people already say they contributed to the DNC... which is The Democratic National Committee. But obviously.. the DCCC is not affiliated with the DNC. So can anyone give me a short brief idea of what the difference is? haha.. thanks everyone!