When you move the mouse around now, a blue line will be drawn from the vertex you just clicked to the mouse pointer. Move the mouse over another vertex and click the left mouse button. Repeat this once more. The order they have been selected in determines which way the triangle faces. If you want the triangle to face the view, then select them in a clockwise direction, and if you want the triangle to be facing awat, select them in an anti-clickwise direction.
Primitives are the name of the group of shapes that are the basic building blocks of stuff.
Using these will be implemented in a later version. Although creating every single vertexl will provide the most control when creating a model, it is also the most time consuming method. There are some extra tools availabe when making models, and these are located in the Modify panel. These tools may not seem very much at first, but they are indeed useful for making models. For definitions of these tool, see the More Complex Editing Section.