The left column includes My Library, which contains all items. Clicking the button above the left column creates a new collection, a folder into which items relating to a specific project or topic can be placed. Think of collections like playlists in a music player: items in collections are aliases (or “links”) to a single copy of the item in your library.
Items can be assigned tags. Tags are named by the user. An item can be assigned as many tags as is needed. Tags are added or removed with the tag selector at the bottom of the left column or through the Tags tab of any item in the right column. Up to 6 tags can be assigned colors and numbers. Numbered tags can be quickly added or removed using the corresponding number keys on your keyboard.
Quick searches show items whose metadata, tags, or content match the search terms and are performed from the Zotero toolbar. Clicking the spyglass icon to the left of the search box opens the Advanced Search window, allowing for more complex or narrow searches.