Do people who make jquery scripts typically edit the jquery.js file? Why isn't there one standard jquery.js file that all people can reference? Or is it the case that each of my scripts uses a different version of jquery?
The reason they include the jQuery file is because that's the file they built there plugin with, more or less what it could mean is that unless you use either the copy they supplied or a newer version the plugin won't work.
The main reason its there is because new users may not know what version of jQuery to use so they supply the correct file for you.
So people don't make changes to the jquery.js files, right? Anyway, I've seen things like "jquery_002.js", "jquery_003.js" and "jquery_004.js" all included in the same package. Why do they use so many jquery files instead of combining them into one .js? Do multiple files load faster than one bigger file?
Personally i have never seen the jquery_002.js thing you have before, the only thing i have seen is developers including jquery.min.js or jquery-1.4.4.min.js for example in their packages.
Ohh, I saw that as well. What is that about? Is it like a snippet of the jQuery library?
It is minified version. It is exactly the same as normal file, but without extra spaces and comments, reducing its file size.
You can just use latest one. Currently its 1.6.1, which you can download from jquery.com. It is backwards compatible with old versions, so if your scripts are written for old versions of jQuery, they should work with 1.6.1 without problems.
Or you can just link to http://code.jquery.com/jquery-latest.min.js that always uses latest version.