What is tempo map?
A record of how the tempo changes across a project, rather than a single fixed BPM. Because DAW positions are measured in bars and beats, anything reading the timeline follows the map automatically.
This is why fixed-speed scrolling fails for music. A words-per-minute prompter drifts against a tempo map; a position-based one cannot.
The moving marker showing the current position on a DAW timeline. Everything time-based in a session is measured against it, which is why a prompter that reads the playhead stays accurate through rewinds and loops.
Beats per minute — the speed of the music. Useful for estimating how long a line of lyrics has to be sung, which is how you tell whether a lyric actually fits the melody before the session.