Star and crescent historically was a symbol of the Ottoman Empire, but later become associated with Islam in general.Now its popularity among Muslims makes it comparable to the Cross and the Star Of David. Many Muslim nations such as Pakistan and Tunisia use it on their national flag.

The Islamic version of the Red Cross is known as the Red Crescent.

Very probably the star in this symbols is Venus.  Venus indeed is often seen close to the Moon.

In Unicode, the "Star and crescent" symbol is U+262A.

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