Found in almost any style of music, 16th note strumming is very common especially among songs with slower tempos.

Practicing this helps us to fill the spaces between songs with lower tempos by swinging the hand to 16th notes.

The key is the ability to identify the groove and to keep the hand swinging! These rhythms are more spaced out and require you to "feel" where the strums land as opposed to thinking in "downs" and "ups"

Good luck!