Band plans exist to guide radio amateurs on the optimum use of spectrum. For effective communications by radio, consideration is needed of many different types of transmission modes available today. Many of these do not comfortable share spectrum with other modes and so spectrum is used optimally if there is some segregation of modes.
IARU Member Societies contribute to the development and maintenance of bandplans. These can be accessed below.
After approval by the Virtual General Conference in Novi Sad 2020, the modifications of the Region 1 HF band plan became effective at 16 October 2020.
The VHF band plans are kept under continuous review and the latest versions can be accessed via the above link