b-tagging is a method of jet flavor tagging used in modern particle physics experiments. It is the identification (or "tagging") of jets originating from bottom quarks (or b quarks, hence the name).

b-tagging is important because:

The methods for b-tagging are based on the unique features of b-jets. These include:

None of the methods of identifying b-jets are foolproof, and modern particle physics experiments must devote significant time to studying how often they successfully identify b-jets and how often they misidentify other jets. Monte Carlo simulations are used to develop and evaluate the performance of tagging algorithms.

Experiments making precise measurements of B mesons (mesons containing b-quarks) also try to identify the particular initial B meson within the jet. This is done in order to observe the oscillation of one meson into another (B⁰
–B⁰
oscillation), which allows the measurement of CP violation.

Martin, B.R; Shaw, G. Particle Physics (3 ed.). John Wiley & Sons.