Pathfinding
Also said as A*, A star, Dijkstra's algorithm
Finding a route through a map. A* is the standard: always explore the most promising spot, judged by distance so far plus a guess at what is left, which finds a shortest route quickly.
Characters that walk into walls are the most visible AI failure there is. A* is cheap for one character and expensive for a thousand, so crowds need tricks such as sharing routes.
Say it
“Use A* on an 8-way grid with diagonal distance as the estimate, and share one path between enemies going to the same place. Limit it to 20 searches a frame.”
Where you’ve seen it
Factorio's biters use A*. Its 2019 Friday Facts #317 explains how a second, coarser search across map chunks now provides the estimate, so they can route round whole lakes in a few ticks.
Not to be confused with steering
Pathfinding plans the whole route ahead. Steering decides the next small movement, such as dodging someone in the way. Most games need both.