From publisher blurb:
Appendix B of the Monster Manual provides a number of generic NPCs that can be used in numerous ways, especially if “re-skinned” in a different role. For example, the bandit NPC on page 343 of the MM can easily work as a brigand, a street tough, a mercenary recruit, and so on. However, while it might represent a pirate, there are better ways to capture that archetype.
The NPCs herein are meant to fill a number of gaps and provide you with a larger variety of characters to inhabit the worlds you create, ranging from CR 1/8 to CR 6.