What is the 3D cursor used for?

A. It's only a visual reference in the 3D View.
B. It's used to align objects and elements to it, and as a pivot point from which to transform
objects.
C. It's useful to indicate a point of interest to your colleagues in a presentation.
D. It's really not very useful, but it makes Blender look different.

B – When you create an object, it appears in the 3D cursor's position, but its main functions
are aligning objects (using the Shift + S menu) and as a pivot point for transforming objects.