"Queue for all checked-out items" is used to place a request on material that is currently checked out by other people. Your request is made for all copies of the same title and will be added to the queue. You have to wait until there is a copy available.
"Request this item" is used to request available copies, either from the closed stacks or from open shelves. Upon request, the material will be collected for you. Please note that you can't request material from open shelves to pick up at the same library. Also, you can't request available course books to pick up at another library.
Material marked as "In house use only" is only for reading in the library.