Temporal subordinate clauses: nachdem, bevor, während

A subordinate clause with nachdem, bevor, or während tells when something happens. The finite verb always goes at the end of the clause, and a comma comes before the main clause.

With während, two things happen at the same time: Während ich koche, höre ich Musik. Here koche is at the end of the subordinate clause.

With bevor, the action in the subordinate clause happens later than the one in the main clause: Bevor ich gehe, schließe ich die Tür ab. First locking the door, then leaving.

With nachdem, the action in the subordinate clause is earlier. It is already finished, so it often appears in the pluperfect, with the main clause in the preterite or perfect: Nachdem ich gegessen hatte, ging ich spazieren.