Meaning
An asterisk on a square key, matching the star key on a phone keypad. The asterisk usually marks a footnote, a note or a correction.
People use it for side notes, terms and conditions, phone menu instructions and as a neat bullet: “*️⃣ Offer valid for dine-in only” In casual chats an asterisk often marks a typo correction, and the keycap version simply makes that note stand out more.