Since Windows 7, File Explorer will show your recent files (maybe documents, music, photos, movies, executable files, or even porn you have opened before [oops :D] ) and frequently accessed folders by defaults. For some people, it will lead to privacy issues and you didn't want it showed. This is how to disable it.
Alternative 1: The easy way
1. Open Windows 10’s Settings app and click on the Personalization icon.
Click on “Start” on the left menus, then turn off “Show recently added apps” and “Show recently opened items in Jump Lists on Start or the taskbar” in the right box.
When you turn off recent items and frequent places, it will clear all recent items from jump lists and File Explorer. Items you pinned, however, will stay in place until you manually unpin them.
Alternative 2: The Tricky Way
For multiple users PC running Windows 10 Pro edition, you can disable through Group Policy. Press “Win + R” to open the Run dialog box and type “gpedit.msc”. Under “User Configuration > Administrative Templates”, click “Start Menu and Taskbar”.
In the right pane, double click on “Do not keep history of recently opened documents” to open the Properties box. To disable Recent Items, choose “Enabled” and click “Apply.” Similarly, double click “Remove Recent Items menu from Start Menu” to disable recent item menu.
Windows 8, 8.1 and 7
Windows 8 and 8.1: Right-click on the taskbar empty area, and click “Properties”.
In the Jump Lists tab, uncheck “Store and display recently opened items in the Start menu and the taskbar” and “Store recently opened programs”. You can even set the number (default is 10) of recent items and frequent places you want to display in Jump Lists and File Explorer.
Windows 7: Right-click or press and hold on a empty area on the taskbar, and click “Properties”.
In the Start Menu tab, uncheck “Store and display recently opened items in the Start menu and the taskbar” and “Store and display recently opened programs in the Start menu”.