DIST(DI) in CAD refers to measuring the distance and angle between two points.

Summary:

Generally, the DIST command reports three-dimensional distances in model space and two-dimensional distances in layouts in paper space.

In model space, the distance and angle changes of X, Y and Z components are measured relative to the current UCS in three-dimensional space. In paper space, distances are usually reported in two-dimensional paper space units. However, when object capture is used in a model space displayed in a single viewport, the distance is reported as a 2D model space distance projected on a plane parallel to the screen.