** Using WeBWorK **

I have a test course set up on our own server which I log on as the professor.
In "Library Browser", I see

Browse:
"Problem Library", "Local Problems" (grayed out), "From This Course",
"Set Definition Files"

or Problems from: "Dartmouth", "Detroit CDS", "Indiana", "Northern Arizona", "Rochester Grade 8", "Rochester", "College of NJ", "Univ Georgia", "Univ Michigan"

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Then I go into Course "maa102" at Rochester and see:

Browse:
"National Library" (grayed out), "Local Problems" (not grayed out)
"From This Course", "Set Definition Files"

or Problems from:
"NPL Directory", "Detroit CDS", "Northern Arizona", "Rochester Grade 8"
"Rochester", "Union"
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So my questions are as follows (remember I'm a complete newbie to this)

1) What's the difference between the "Browse..." and "Problems From..." buttons?

2) Why do I see different problem libraries in different courses? Does that just mean that my department has one library installed and not the other, and both of these are components of the NPL?

3) When I click on "NPL Directory",when I see see items like "Rochester\SetAlgebra14Lines" and "Dartmouth/SetStewart15". Are these sets that have been added to the National Library, and the same goes for the "Detroit CDS" and "Northern Arizona"? In other words, the NPL is just all these other libraries collected in to one place? So for example, I'll see a button for "Dartmouth" in my school's page, and one for "Rochester Grade 8" in another site. Does that mean that my server admin put in links to these parts of the NPL and not others?

4) When putting together my own problem set, then assuming I have access to either NPL or the library within NPL that these came from, I can just pick problems from each set and "mix-and-match?"