Meaning
The kanji 月 on a square button, meaning moon or month in Japanese. As a button it stands for a monthly amount, like a fee or subscription paid each month.
It suits talk about rent, phone plans, memberships and monthly budgets: “Gym membership 🈷️ is going up again” Because the character also means moon, some people use it for night or moon themes, though 🌙 is much clearer for that.