For tips on timing beatmaps, see: How to time songs
A timing section in the beatmap editor denotes a change in the timing (e.g. offset or BPM) of a beatmap. Beatmaps can have a single timing section that takes up the whole song or many timing sections that are split up throughout the song.
When the tempo of a song changes, creators are required to add a new timing section to accompany the new tempo. A beatmap that uses incorrect timing will not be considered rankable.