标识 (biāoshí) is a general word for any mark, sign, or label that identifies something. As a verb it means 'to mark or label'. It overlaps heavily with 标志 (biāozhì), but 标志 is more often used for a symbolic emblem or logo, while 标识 is broader and more practical (e.g., road signs, product labels). 标签 (biāoqiān) is specifically a physical or digital tag/label, and 商标 (shāngbiāo) is a registered trademark.