A “bot lobby” is a group of unskilled players that are unable to play successfully. The best Warzone VPNs give you access to these bot lobbies, making it easier for you to climb the leaderboard and gain experience without ruining your kill/death ratio.
SBMM is skill-based matchmaking, which means that you will only usually be pitted against players of a skill set that is similar or greater than your own. Although the creators of Call of Duty: Warzone and Warzone 2.0 have never officially confirmed the existence of SBMM, it’s hard to dispute its existence. There has been plenty of testing online that proves players are consistently placed in lobbies with others of the same or greater skill level.
Splitting playlists between a ranked mode with SBMM active and a casual mode without SBMM is a compromise that many players would like to see happen. However, there’s no word from the developers on whether this might happen.