any differences between "crown" and "tiara&qu

the queen said to the photographer that what she was wearing is not a crown but a tiara.
any difference between them?

cheers

According to my dictionary, a "tiara" is a small crown.

But from the pictures I've seen, tiaras are shaped differently from crowns, and to me a "tiara" tends not to carry the same connotations of sovereignty as a "crown."

kinda got the picture, thanks!