Construct a segment between two points. The points do not need to exist, they will be constructed, as soon as you click on an empty spot.

Construct a segment. You also need to points for that.

Construct a triangle. You need three points for that.

Construct a vector. A vector is segment with a direction. You need a vector to move a point.

Construct a ray.

Constrcut a parallel line. You need to click on an existing line and then choose a point through which the parallel line should run.

Constrcut a perpendicular line. You need to click on an existing line and then choose a point through which the perpendicular line should run.