Well, look, “rofl” comes from the English abbreviation “ROFL”, which means “rolling on the floor laughing”, or, to put it simply, “rolling on the floor with laughter”. Imagine someone laughing so hard that they just fall to the floor and can't stop. That’s what rofl means: very strong laughter from something really funny.
Rofl is mainly used on the internet or in conversations when something really funny and nice (that is, cool or awesome) becomes the reason for a good mood. For example, your friend sends you a meme about a cat that falls off a chair in a funny way, and you’re not just smiling, but laughing so hard that you want to say: “That’s a rofl!” — this means that the situation has caused you very strong laughter.
So, a rofl is those moments when something is so funny that you can barely contain your laughter, and it’s not just nice, but a real rofl.
