Quickly find the repeating themes between your notes and your friends' using the filter pane, which can be found in the sidebar. There are a few default filters;
Mine - cards you have authored
Liked - cards you have liked
Kept - cards you have kept
Priority - cards marked as 'priority'
Visible - cards marked as 'visible'
Invisible (on by default) - cards marked as 'invisible'
Published - cards which are published
Archived (on by default & only available in parent cards) - cards archived within a parent.
The default filters cannot be removed, and always appear at the top of the filter pane. You can also add your own tag or user filters by using the
+ add new filter button. Or you can enable/disable a tag filter simply by clicking on the name of the tag on a card, like in the example below:
When a filter is active in the filter pane it will be highlighted and a switch will be present. By default the switch is a right arrow, an 'inclusive' filter, but you can click it to switch it to be an 'exclusive' filter i.e. it will remove any content associated with it.