Several months ago, in response to the Black Lives Matter movement, GitHub undertook to rename the default branch name of its repository from master to something with less racist overtones.
Recently the company discussed the progress it made to implement this, and announced Main will be replacing Master on the 1st October 2020.
GitHub has first tested the changes internally but by the 1st October all newly-created repositories will default to main and any new repositories you create will use main as the default branch, instead of master.
Existing repositories will continue to have the same default branch they have now, but GitHub will be offering a tool to allow seamless renaming by the end of the year.
GitHub is not the only repository making the change, with the Git project itself leading the change at a number of vendors.
While the move may be seen as reactionary, it is notable that the Drupal project in 2014 already started deprecating the term Master, followed by Python, Chromium, and the PostgreSQL and Redis database systems.