Unharmed means not hurt, not injured, not damaged — used about someone or something that came through a dangerous situation with nothing wrong. The important thing is that unharmed almost always needs danger nearby. You would not look at a healthy friend walking down the street and say "he is unharmed". You say it about the passengers after a crash, the hostages after a rescue, the house after a fire, the paintings after a flood. The word quietly implies that something bad happened and this person or thing escaped it. That is why it lives so naturally in news reports: "All four crew members were rescued unharmed." Grammatically it is flexible. It sits after the verb be — they were unharmed — and it also works as a kind of extra comment tagged onto a sentence: she walked away unharmed; the child was found unharmed. It very rarely comes before a noun; "an unharmed child" is possible but sounds odd, and native speakers would usually say "the child was unharmed". You will also hear the fixed pair safe and unharmed, which is a little repetitive but extremely common in reporting, and physically unharmed, which is doing something specific and rather sad — it means the body is fine, and gently suggests the mind may not be.