Which two points of concurrency always remain inside the triangle, and why?

The point of concurrency is the point where three or more lines, segments, or rays intersect forming a point. Out of the four namely the Centroid, Incenter, Circumcenter, and Orthocenter, only the Centroid and Incenter is always located inside the triangle.

Centroid: where the medians intersect

Incenter: where the angle bisectors intersect