Now that our profile is a mesh, you will be working in terms of vertices, edges, and faces. Vertices are the points that make up the edges. Edges, in turn, are the borders that make up faces. In 3D printing, the slicing software is ultimately concerned with the faces of your object. An object with just vertices and edges would not print.
When you are in Edit Mode, you have the ability to view and edit all three elements of a mesh. There are now icons at the bottom of the screen that will let you switch your Selection Mode. If you select the leftmost icon, which is a yellow point on a cube, you will be in Vertex Select mode, where right-clicking will select specific vertices in your model. Selecting the middle icon, a yellow line on a cube, will put you in Edge Select mode and allow you to pick the edges or the outline of our profile. There...