You can create axes when you need a reference or snapping point for your sketch, when there’s no edge available, when you need an axis to use a transformation tool, or when you need to create a substitute edge for a filleted edge. 
The axis type is broken down into these:
-
Through 2 points
Select two points, and an axis will be created between those points. -
Through 2 planes
Select two closed sketches, faces, or planes, and an axis will be created at the intersection of the two selections. -
Through edge
Select an edge of a body or a line in a sketch, and the axis will be created on that edge or line. -
Perpendicular to face at point
Select a closed sketch, face, or plane, and then select any where in your design space. An axis perpendicular to your selection will be created from that point. -
Through a cylinder or cone
Select a cylinder or cone, and the axis is created through the selection, overlapping with the body’s axis of rotation.