I'm hoping somebody can help me. We are considering allowing another department
to host material on our website. We'd like for them to upload their content on
their own so that we don't need to be bothered. However, I worry about them
overriding, deleting, changing, etc our existing files. Is there a way that I
can "lock" our folders so that they can't change anything? Or is there a way
that I can give them access to only one folder? When I right click a folder I
find the Permissions option but it's not very intuitive.

Where I work, the network "folder" is owned by the Division, but I need to be
able to update or add content for my Department

So, the IT folks created a network permission that I may do anything at all
inside that folder... with files that begin with the 5 letters that indicate
the file belongs to "me" and not to the "folder owner"

You own the website, so you put in a permission that "someone" or "anyone"
else may add or update or delete files... as long as they begin with FinDept
(or whatever you need as identity)

I have no idea how our IT staff created the permission rule for me... I just
know that as long as I put our 5 letters on the front of the file, I may do
anything I want to just those files, and not do anything at all to any other
file