If you want to open a database that you have previously opened, then a quick way to open the database is to use the Recent File List
From the "File" group, Click the "Recent Files" button

From the list, simply click the file you wish to open.
File List Maintenance
The Recent File List remembers the last 9 files that you opened, after which the last entry is dropped so the the list never get longer than the last 9 files.
If you want a file to stay on the list irrespective of how many files you have opened then, you can "Pin" the file to the list using the pins on the right.
In the list above you can see that entries 8 and 9 are pinned and will not therefore be dropped when another new file is opened.
If you select an entry and that file cannot be found, it will also be removed from the list, unless it has been "pinned".