what is the difference between a ringtone and a ringback tone?

Ringtones are downloaded to your wireless phone.  With ringtones, you hear a chosen song instead of a standard ring through the phone when receiving calls.

With ringback tones, you choose a song for the caller to hear instead of the usual ringing before you answer the phone.  Ringback tones stay on the Cricket network so if you ever change phones, you can still use the ringback tones you have already purchased.