Bookmarks- the word is self explanatory. You make selections in your dashboard and put a mark to get back to it later on.
For example, You select date range from DATE list box, then you pick region from REGION field and finally you select a SalesPerson from SALESPERSON list box and so on. You can save all this selection under a bookmark and save it for future reference. You won't have to manually select the same selections again. You can also send this bookmark to some other users if you are trying to explain some business issues based on this selections.
Hope this throws some light on the usage of the bookmark.
