Before recording begins, the dubbing studio receives a copy of the audio elements to be used in the show. These are at the very least 1. a complete mix in the original language (to serve as a guide), and 2. a mix of everything except dialogue, known as the M&E (Music and Effects) mix, which is invaluable when planning the recording schedule.
Strictly speaking, the M&E does not include any human sounds, but an M&E produced specifically for a foreign language dub can include location ambiences, crowds, breathing, screams, effort sounds, sneezing, whistling, and any other non-verbal human sounds. Ideally these will be provided on a separate Optional track that may also contain songs if the show features any singing characters.
When the M&E is assessed, everything than can be re-used from the optional track is marked, and consequently will not have to be recorded in the studio. This will save a production considerable time, particularly in an action movie.