LitRPG

These are stories in which RPG mechanics play a role: the characters level up, or have game-like skills, or something similar, and this happens within the context of the story. So someone in a fantasy setting might go to join the Adventurers' Guild and be told that they need to be at least level 5 to apply.

This is quite common in isekai stories. The protagonist will often use prior experience playing games to exploit loopholes in the RPG system of the new world, or else just set to grinding (as in So I'm a Spider, So What?).

Sometimes, access to the RPG system will be limited to only the protagonist, or other people summoned from the 'real' world. A non-isekai example is The Skeleton Soldier Failed to Defend the Dungeon.

The webtoon The Gamer is a typical example.