What is the difference between a dimensional constraint and a constraint parameter?

[QJaworski]

In the block editor, I see how to use dimensional constraints easily enough, but I do not understand what constraint parameters are. In particular, if I have a list of dimensional constraints in the parameters manager, what benefit do I have by converting any to a constraint parameter?

[j.palmeL29YX · Accepted solution]

With Dimensional constraints (created with the Dc... commands) you can drive the dimensions of any geometric objects . Changing the value of a Dimensional Constraint changes the dimension of the associated geometric element (e.g. its length, or diameter/radius, or angle, ...) or the relative position of the geometric elements to each other, usual in combination with geometric constraints.
These can be used in the standard environment of AutoCAD as well as inside the block editor. That means, you can use dimensional constraints to drive the geometry inside of the block editor.  They are used to fix geometry while building the block definition. In the inserted block references you will not see this constraints and can not change their values,
At the other hand: In the block editor (and only here) you can add constraint parameters (bcparameter command). They work similar to the dimensional constraints, but they are also visible in the block references (either their grips and/or listed in the properties window) and are used to change the associated geometry at the inserted block references (similar as the dynamic parameters and actions do. But you should avoid to mix both methods to drive the geometry of block references). 

[QJaworski]

Thank you! This clears it up for me.