How does the Import from Clipboard feature work?
Import from Clipboard allows you to import items from the raw code of any supported format (RIS, BibTeX, CSL JSON, etc.).
Whenever you're viewing raw bibliographic data, you can import it into Zotero simply by copying it to the clipboard and then choosing “Import from Clipboard” from the File menu in Zotero or by using the keyboard shortcut (Ctrl-Alt-Shift-I (Windows/Linux) or Cmd-Option-Shift-I (Mac)).
See Importing Standardized Formats for a list of supported formats.
Note that, on most websites, you should use the Zotero Connector's “Save to Zotero” button to save data and files to Zotero rather than importing metadata directly. See Adding Items to Zotero for more information.