Not triangulation - but confused for it. Positioning yourself by looking at distances to 3 known objects.
If you’ve know you’re a certain distance from a point, you may be anywhere on the circle surrounding that point (see the pink line below). If you know the distance between you and two points, you are at one of two possible places, where those circles intersect. If you add in a 3rd distance to a 3rd known point, then you’re able to determine an unambiguous location.
This is how GPS works.