Extrusion tools duplicate vertices, while keeping the new geometry connected with the original vertices. Vertices are turned into edges and edges will form faces. Use this tag for questions about extruding vertices, edges, or faces.
The version 2.80 manual described extrude thusly:
Extrusion tools duplicate vertices, while keeping the new geometry connected with the original vertices. Vertices are turned into edges and edges will form faces.
The current manual simply lists the possible extrusions in mesh edit mode and points to their individual web pages:
Use this tag for questions pertaining to any of those forms of extrusion.
