Begin with a brief description of the band's genre. Keep it to one sentence.
Note the most important things you have accomplished as a band. If you are approaching a label and you have significant sales success in a region or in a niche, use that information to get the label's attention. If you have played major venues, go with that.
Follow with more impressive stuff. If your bass player was a studio musician for a famous artist, list that. This is the place to name-drop without bragging; just let people know that you are pros.
List prior bands and accomplishments of musicians in other groups if appropriate. This can connect you potentially to someone the reader may know. The more connections readers can make, the more impressed they may be and the more they will feel they know a bit about you. You may not, however, want to mention that you have been a professional musician for 35 years if your target demographic is 18- to 24-year-olds.
Provide a list of influences to help the reader understand where your sound comes from.