Meaning
A single grey or dark silhouette of a head and shoulders, the kind of blank outline that stands in for a person with no photo. Its literal meaning is simply a person, unnamed.
It works as a profile or account icon in menus and lists, a placeholder for a contact, or a way to mention someone anonymously. Example: “👤 New member joined the group, please say hi”. For more than one person, the paired version 👥 fits better.