There are two questions about SolidWorks.

1. Why is it good practice to fully define

sketchgeometry?

2. Describe what happens if you do not select a planeprior to

clicking on the Sketch icon when creating a sketch.

1. It is a good practice to fully define a sketch to avoid having erroneous dimensions on the faces of a solid, this avoids that when it is required to make an assembly with the drawn part appear assembly errors.

2. The 2D sketch should always be done on a plane, so solidworks would ask you to select a plane on which you want to make the sketch, on the other hand, if it is a 3D sketch, solidworks allows you to do it without the need for Select any plane.