Edges are the lines that are created when you connect two vertices. Edges are not rendered unless the Wireframe setting is on. Three or four connected edges are necessary to form faces.
Appearance[]
Edges are one-dimensional lines that can be several different colors. In Edit Mode, they are either black or yellow, depending on whether or not they are selected. In
A cube in Edit Mode with 4 selected edges (yellow) and 8 unselected edges (black).
Object Mode, they are invisible if the edges have faces. However, if the edges don't have faces, they can be seen as black (when the mesh is not selected) or pink (when the mesh is selected). They can also appear as green lines if their mesh is a member of a group.