What is a band plan, beyond the privileges established by the FCC?

The FCC sets strict rules about which license classes can operate on specific frequencies. However, to keep different types of signals (like CW, SSB, FM, and digital) from interfering with each other, the amateur radio community has created "band plans." A band plan is a gentleman's agreement or a voluntary guideline that organizes activities within the amateur bands. It suggests specific slices of a band for specific operating modes to ensure orderly and efficient use of the spectrum. Because it is a community-driven agreement, it is not legally enforceable by the FCC in the same way as Part 97 rules, making it strictly voluntary. Distractors suggesting it is an FCC mandate, a net schedule, or just a local club rule miss the broad, voluntary nature of these guidelines.