Master is the highest rank division, and to get there you'll need to earn RP from matches that can raise or lower your rank tier, and potentially even knock you down a division. At the end of the season, you'll get a reward based on your highest placement.
The update also marks the dreaded arrival of bots. They'll start appearing in regular games, but not ranked matches, and are apparently designed to give players a few easy kills to help them hone their skills. PUBG Corp acknowledged that bots are a "controversial" feature, and so far the addition has not exactly been welcomed with open arms.
You can check out the 7.2 update now. Take a look at the patch notes for the full list of changes.