But in a nutshell, Scottish Country Dance is very buoyant, you dance on your toes with lots of upward movement, and it's the best of these three in terms of physical exercise! The bounciness gives it a particular look which I think is unique to Scottish Dance (including the Country dance as well as Highland dance, which is quite different and is mentioned below briefly).
In general, I have difficulty doing substantial improvising while dancing, so I dance the kinds of dance that are specified -- there's a particular thing you're supposed to be doing. Of course, you might not necessarily do that exactly right, but that's what you're aiming for; you don't have to decide which move or figure to do next; that's prescribed, as you are dancing a particular dance. There is still some room for creativity, but you don't have to decide which figure to do next, you have to remember it.
Almost all Scottish Country Dances are danced in set lines with the women down one side and the men down the other side, and you are across from your "partner". This is common also to English Country Dance and Contra Dance (although there are a number of English Country Dances which are danced in other formations).
Here is a fairly typical type of Scottish Country Dance:
Here is a dance which I think looks particularly cool ("Shiftin' Bobbins"):
This is my favourite dance video (this is a medley they put together for
this special performance, adapting all the dances for different numbers
And the other kind of Scottish dance you've heard of, which isn't Scottish
Country Dancing but is known as Highland Dancing:
The Highland Fling (incomplete): http://www.youtube.com/watch?v=emCIxAJCe2g
Here are instructions for almost all of the thousands of Scottish Country Dances, with links to Youtube videos for many of them (the links to videos are in the third section on the page for the particular dance, if there are any known): http://www.scottish-country-dancing-dictionary.com/dance-cribs.html
One way to start is with lessons.
The first lesson is free.
See http://www.dancescottish.ca/Lessons.html .
You can go to a "Introduction" class, or even if you are a raw beginner I'd say you could start with the first, second, or third "beginner" class in the fall, or the first or second one in January.
The "dancing in the park" events in the summer are a good introduction as they are very casual, with lots of people just watching, and you can dance just some of the easier dances, or none, as you like.
The Toronto Scottish Country Dance community is very nice and welcoming and encouraging. You'll be happy that you came by... and so will they!