For something to be "lit" or "fire," it means that something is great, amazing, exciting, etc.

What does ? mean in texting?

The fire emoji is a flame that is mostly yellow with a little red on the top. It is used to signify that something is cool, awesome, exciting, or more colloquially, “on fire.” It can also convey that someone is sexy, (i.e., hot), or refer to other various metaphorical fires.

What does become fire mean?

to dismiss from employment, a post, or other job; to cause (a person) to cease being an employee; -- of a person. The act of firing is usually performed by that person's supervisor or employer. Fireverb.