Calibration:

Calibration is the process Dota 2 uses to place a player into ranked matchmaking by estimating their skill level from a set of ranked games and assigning or adjusting their MMR and rank. It matters because those early results shape where a player starts in the ranked system and how quickly the game matches them with opponents of similar skill. Calibration is also used when the system has limited confidence in a player’s rating, so each result can move the estimate more strongly than in ordinary ranked play. For example, after a new account completes its calibration games, a player who performs well may be placed into a higher medal bracket than someone whose games go poorly.

Related: MMR