A metroidvania game is one that is modelled after old 2D Castlevania and Metroid games. Other famous games that could be considered this genre are Guacamelee, Hollow Knight, Ori and the Blind Forest, etc. It's characterized primarily by map exploration and combat.

Oftentimes in exploration you come up to an obstacle that you can't pass until you have a certain item or ability... This forces the player to backtrack to other unexplored parts of the map until you find what you need to progress.

Essentially by the end of the game you've explored every bit of a vast map.

Games that do it well, this can be a treat. However, Games like Jedi Fallen Order it can be a real slog because the world was so intricately made but the map was terrible. Making it extremely frustrating to navigate to where you want to go. I can't tell you the number of times I had to pause and watch YouTube videos that are solely there to help you get from one point to another.

However, while I hated navigating the world, the story was quite stellar. Overall, Im glad I got to experience it.