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.). Many websites post the bibliographic data for items in their raw form. To add these items to your Zotero library, select and copy the code from the site, then import through the option in File menu in Zotero, or by the keyboard shortcut (Windows/Linux: Ctrl-Alt-Shift-I / Mac: Cmd-Option-Shift-I).
See here for a list of supported formats.