Visio 2000, other low-end CAD fer a laptop....

The basic idea is that internally, if an old-style nonparametric CAD program calculates some quantity (say, the length of something-or-other), it then stores the resulting quantity. A parametric CAD program stores the recipe for performing the calculation.
So instead of a variable in your design being stored as, say "the length is 100mm", it's stored as "the length is equal to the length of bolt A minus the width of nut B". This means that if you resize bolt A, any part of the design that was calculated from its dimensions changes appropriately, rather than you having to go back and change it yourself. In both programs, there is a feature to calculate the length (100mm) from the length of bolt A, and the width of nut B; the difference is that the parametric program remembers how it calculated it.
(My understanding of this comes largely from talking to someone who had worked as a programmer at Parametric Technology, which was the company that basically invented the concept.)

=A0 =A0 =A0 =A0 =A0 =A0 Hide quoted text - I agree with Norman in a quite academic sense. The way I differentiate the two practically is the overall focus of the user.
So.. What does the OP do?
In my experience, parametric for assemblies, drafting for parts. (This potentially changes for complicated parts with 3D features, however. Not something every user has to worry about though)
I learned on AutoCAD in highschool. Still applies today. Making beautiful engineering drawings of single parts that a tradesperson can build is best done in CAD. Total control over every portion of every line. Just the way it ought to be.
Building assemblies (tooling, machinery, complex products, etc.) is far and away superior in parametric modeling. Assemblies are a total gong show in drafting software. Too cumbersome to make, too cumbersome to change. Not worth the time. Would rather widdle them out of sticks.
I bought Alibre because I am a tool maker and I need to design assemblies (dies and machinery) and I need to see collisions and how things are going to go together. Ultimately I do have to produce working drawings, but mostly just for myself which is acceptable with Alibre. I can make pretty good working drawings for outside contractors with Alibre, but drafting software would be superior if it was my main focus.
Just my $0.02 worth.
Regards,
Robin

I agree with Norman in a quite academic sense. The way I differentiate the two practically is the overall focus of the user.
So.. What does the OP do?
In my experience, parametric for assemblies, drafting for parts. (This potentially changes for complicated parts with 3D features, however. Not something every user has to worry about though)
I learned on AutoCAD in highschool. Still applies today. Making beautiful engineering drawings of single parts that a tradesperson can build is best done in CAD. Total control over every portion of every line. Just the way it ought to be.
Building assemblies (tooling, machinery, complex products, etc.) is far and away superior in parametric modeling. Assemblies are a total gong show in drafting software. Too cumbersome to make, too cumbersome to change. Not worth the time. Would rather widdle them out of sticks.
I bought Alibre because I am a tool maker and I need to design assemblies (dies and machinery) and I need to see collisions and how things are going to go together. Ultimately I do have to produce working drawings, but mostly just for myself which is acceptable with Alibre. I can make pretty good working drawings for outside contractors with Alibre, but drafting software would be superior if it was my main focus.
Just my $0.02 worth. =================================================
Inneresting and cogent distillation.
But, if Alibre can do assemblies, why wouldn't it be able to do a bang-up job on drafting-type drawings? Too much drama, given its horsepower, for simpler tasks? Or does it really just produce merely "acceptable" working drawings? Why?