The short description for charm says: "A humanoid becomes more friendly to you"
However the full spell text says "targets 1 creature", and doesn't mention a qualification, which is odd. In 1E we were always told to take the full description as the correct one.
The short description isn't rules text, it's just a short explanation of what the spell does. Kinda weird that it specifies a humanoid - I'm assuming this is either a remnant of some early version of the rules or a typo.
Anyway, it works on any creature, not just a humanoid.
I believe it’s one creature, and the humanoid flavortext is a holdover. Note that Charm Animal is gone, and that the Primal List has Charm now, which has me believe that Charm Person, Charm Animal, and Charm Monster all got folded into Charm.
All the variations of charm that existed in previous versions of the game (charm person, charm animal and charm monster) have been merged in this new edition, so that it can affect ANY creature that's not immune to it.