Boosting in Rainbow Six Vegas 2 is a technique used to quickly and easily level up your character, as well as gain access to better weapons, gear, and abilities. It involves having a higher-level player join your game and help you complete missions on a higher difficulty setting, which grants you more experience and rewards.
Boosting can be beneficial for players who want to quickly level up their character, unlock new weapons and gear, or complete the game on a higher difficulty setting. It can also be helpful for players who are struggling with a particular mission or boss fight.