What does anyone mean?

The term "anyone" refers to any unspecified person, as if chosen from the defined population at random. When applied negatively, it becomes "no one" or "none".

Example : "Is anyone at home today?" (i.e. anyone who resides there ordinarily)

Example : "The culprit could be anyone in the room."

Example : "Don't trust anyone." (equivalent to "trust no one")