Vice.com's Why We Use “lol” So Much talks to a linguist who's studied how internet users are using "LOL" in online, text-based conversations. LOL may have began as an interjection, but one linguist says that it's often used as a discourse marker or pragmatic marker. A discourse marker is a word that
help[s] structure a sentence, or orient fragments of text to context, and past or upcoming sentences. Pragmatic markers, on the other hand,
communicate a person’s attitude, and enhance the meaning of a sentence, without being specifically descriptive of that meaning.
As the piece explains further:
In the YouTube comments, [Célia] Schneebeli found that the positioning of lol in a sentence affects its meaning. When lol is at the end of a sentence, it’s more often a pragmatic marker. When used in isolation—which Schneebeli called a “standalone lol”—it has a more simple expressive role: it communicates a reaction, like amusement.
One of the more intersting things that Schneebeli found is that similar expressions — LMAO, ROFL, and my personal favorite ROFLMBAO — are used more literally. In other words, LOL probably no longer means that someone is literally laughing out loud, while ROFL probably does.
Still to be determined: whether emoji such as 😂 and 🤣 will take the place of our laughter-indicating acronyms.