It is a corner: a point where three of more faces meet.
In a 3-dimensional shape with polygonal faces, an edge is a straight line at which two faces meet. A vertex is a point where three or more edges meet. In solid shapes which are not polyhedra, an edge is still a line - possibly curved - where two faces meet. But a vertex can be any corner, for example, the point of a cone.
That's a "vertex".
It is the vertex and its plural is vertices
Polyhedron. It's any three-dimensional shape made up of flat faces, sharp edges (where two faces meet), and points (where three faces meet).