Meaning
A smiling face crying big tears of laughter, eyes shut in happy arcs. It stands for laughing so hard you cry, and over time it has also become a general “lol” that people add to almost any amusing line.
It fits funny stories, memes and teasing between friends: “I just called my teacher ‘Mom’ in front of the whole class 😂” Since it shows tears, some readers, especially older relatives, may at first take it as sadness, so context helps. Some people also see it as a slightly dated way to laugh and prefer 💀 or 😭 for the same feeling.