Exclamation mark

The exclamation mark (Commonwealth English) or exclamation point (American English) is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or high volume (shouting), and often marks the end of a sentence. Example: “Watch out!” Similarly, a bare exclamation mark (with nothing before or after) is often used in warning signs.

The mark can also be used at the beginning of a word instead of at the end. For example, several computer languages use "!" for logical negation; e.g. "!A" means "the logical negation of A", also called "not A". There are many other specialized uses of this mark, such as in mathematics where it denotes the factorial operation.

https://en.wikipedia.org/wiki/Exclamation_mark