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. On an ellipse it sizes one semi-axis at a time.
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.
Offset
offsetFrom holds one or more entities at a distance from the entities they were offset from — a line parallel to its source at that distance, an arc or circle concentric with its source at its radius plus or minus that distance. It is the dimension the Offset tool writes: the offset curves are ordinary lines and arcs you can pick, dimension and constrain further, and this one statement keeps them following the outline they came from.