It’s both. Each emoji has a pictographic meaning as defined by Unicode, but there’s also a language that has arisen contextually on social media. For example the “painting nails” emoji may refer to painting one’s nails, but it can also mean “whatever” as in “whatever you say I’m just painting my nails”.
Or the skull emoji which has a variety of meanings relating to being metaphorically dead - “I’m dying from laughing”, “you’re fucked”, etc.
There’s also the controversy over the acceptability or not of using the sobbing emoji to represent laughter.
