The dialogue editor assembles, synchronises, and edits all the dialogue

Dialogue

Dialogue is a literary and theatrical form consisting of a written or spoken conversational exchange between two or more people....

 in a film

Film

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

 or television production. Usually they will use the production tracks: the sound that was recorded on the set. They will smooth it out in terms of volume and equalisation. If any of the production tracks are unusable they can be replaced by either alternate production tracks recorded on set or by ADR, automated dialogue replacement, which is recorded after the shoot with the actors watching their performances in a sound studio and rerecording the lines. Large productions may have an ADR editor working under the dialogue editor, but the positions are often combined. The ADR editor or dialogue editor also work with the walla

Walla

In American radio, film, television, and video games, walla is a sound effect imitating the murmur of a crowd in the background. A group of actors brought together in the post-production stage of film production to create this murmur is known as a walla group...

 group in films which they are required, providing the background chatter noise in scenes with large crowds, such as parties or restaurants.

Once the dialogue editor has completed the dialogue track, the re-recording mixer then mixes it with the music

Music

Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...

 and sound effects tracks to produce the final soundtrack.