On July 9, 2019, Niantic announced that many Pokemon will be receiving new moves in an effort to make Trainer Battles more interesting.
Starting on the next update, these Pokemon will learn new moves:
In addition, two new moves will be added to the game: Charm, a Fairy-type fast move, and Skull Bash, a Normal-type move that lowers the user's Defense.
UPDATE: It seems as though some trainers have received the new moves ahead of this update's release. Several players have uploaded images of their own Pokemon with Charm, currently in the game as move_name_0320.
After a brief moment of the moves being unavailable again, it seems as though they are indeed obtainable.
Full Announcement Text
In our previous Community Note, we outlined some changes that came to Pokémon GO that affected your Pokémon’s performance in Raid Battles, as well as other additions to the game. In this update, we’re excited to announce more changes, focusing on Trainer Battles!
In a continued effort to make Trainer Battles a fun and competitive experience, switching Pokémon will now briefly pause the battle. This will grant you more time to choose which Pokémon to call out, and it will avoid Pokémon causing damage to each other while they are withdrawn into their Poké Balls. Charged Attack gameplay will also be updated with new, fun swiping and tapping mechanics. (Want to know more? Check out our Niantic Help page for more info.)
More attacks will also be coming to Pokémon GO!
The following Pokémon will be able to learn attacks they couldn’t before:
Attacks New to Pokémon GO
Certain Pokémon will soon be able to learn attacks that hadn’t yet been seen in Pokémon GO!
We’re excited to see the teams you build with these changes, Trainers. Stay tuned, as we’ll be sharing more updates like these in the future. Good luck on the battlefield!
—The Pokémon GO team