When you activate multiple tags, you can decide if you would like to view tagged items in intersection mode or union mode.
Intersection mode - view items that are tagged to all of the activated tags
Union mode - view items that are tagged to any of the activated tags
The default mode is the intersection mode. To toggle between the two modes, click on the button with two circles at the top right-hand corner of the tag pane.
Click onto switch to the union mode.
Click onto switch to the intersection mode.