The Mendeley Desktop library is divided into 3 sections.
2. Left Column
On the left are your collections, including 'All Documents' (everything in your library) & any collections that you've created.
Below your collections are the different ways that you can filter your references (by author, author keyword, your tags, or publication title).
3. Center Column
In the center are your references, which you can view either as a table (Fig. 1) or as a list of formatted citations (Fig. 2). Choose between these 2 views under the View menu.
Note that you can mark references as Favorites or as 'Read' (a gray instead of green dot).
The PDF icon will appear if there is a PDF attached.
4. Right Column
On the right you can view details of each reference, add tags & documents on the Details tab, & add your own notes on the Notes tab.
Note the Type box at the top of the Details tab, which indicates the type of reference (Journal Article, Book, Web Page, etc.) for each item in your library.
'Tags' are your own search terms; 'Keywords' come from the reference record.
'Catalog IDs' let you look up & import articles using one of these identifiers. Just add the number & click the magnifying glass to pull in the record.