When used related to WesternChess
generally means the process of seeing a game position on the board and discovering what the board looked like previously. There's a book by Sir Arthur Conan Doyle with Sherlock Holmes solving a mystery based on chess problems solved by RetroAnalysis
which is quite good. They generally entail problems such as-
"Figure out which piece the blob is"
"Figure out who's underpromoted, what to, and where it is now"
"Where was that piece five moves ago?"
"What square is that piece supposed to be on?"