Distance
distance is the general linear dimension: point to point, point to line, line to line, or anything to a circumference. Dimensions are constraints with a value — they do not just relate two entities, they hold the relationship at a number, and that number is what you edit later.
Diameter
diameter sizes a circle — the number a drawing carries for a hole or a shaft.
Radius
radius sizes an arc — a rounded corner, a fillet in the profile, a cam lobe. It is the dimension that completes a tangent arc.
Angle
angle holds the angle between two lines, in degrees. Against a sketch axis it sets a line's absolute slope; between two sketched lines it sets their relative opening.