Meaning
A content smiling face wearing a glowing halo above its head, the cartoon sign for an angel. It expresses innocence, good behavior or feeling blessed, and is just as often used tongue-in-cheek.
Sincerely, it suits gratitude and pride in doing the right thing: “Finished all my chores before noon 😇” Playfully, it pretends innocence right after something mischievous, like claiming you have no idea who ate the cookies. Readers usually catch the irony from context, but pairing it with an obvious confession makes the joke clearer.