A Cue Point is a marker on the track that, when triggered, takes you to that position in the song. 

Serato DJ for iOS has 4 Cue Points available on screen for each deck by default. 

Cue Points 5 to 8 are not available in Free mode.

NOTE: Your Cue Points are saved to the file and recalled the next time it is loaded. 

Cue Point functionality can also be controlled using the Hot Cue pads on your Serato DJ hardware.