Pretty much yeah.
Normally when you install windoze you only create 1 partition: C:
Occasionally (and more and more lately) some of the prepackaged PC's will create a second partition for you: D:
This is good because for people like you who wanna ditch windoze but don't wanna lose their files, they have an easy backup solution.
So, if you've got 2 windoze drives (C: and something like D: ) they you can copy all the data to the D: partition and format your C partition and lose windoze without losing your precious files. However, if you format your only partition it's likely you'll lose all the files that existed on it (there are some recovery abilities, but those are usually highly expensive or not worth the effort for the average user).
Best bet is to backup first, then attempt whatever you are thinking about
As for learning about partitions, do a search on:
primary secondary extended logical
On this site and google.com and google.com/linux
There will be TONS of info on partitions and what they mean/do.