  Top tagging is a recent approach to identifying boosted hadronic top quarks.
It avoids reconstructing individual top decay products and instead uses a jet
algorithm to reconstruct the entire top decay. Quite generally, geometrically
large jets including heavy particles (fat jets) can be analyzed on the level of
their subjet constituents. LHC data will soon allow us to establish this new
analysis method. We discuss different tagging algorithms, their critical QCD
aspects, and currently available experimental results. For the development of
taggers and their different applications this review should provide a firm
theoretical and algorithmic background.
