An exclamation mark (!) is a punctuation mark. It is used to show strong emotion at the end of a sentence or after an interjection.
The use of a space in before an exclamation mark is incorrect.
In coding, "!" sometimes means not. In Mathematics, the use of an exclamation mark can be used for the function factorial.
Images for kids
Trilingual billboard in Barcelona (detail), showing the initial exclamation mark for Spanish, but not for Catalan (top line) and English.
This Action Comics cover from 1959 ends every sentence with an exclamation point or question mark. Often, few or no periods would be used in the entire book.
New Zealand road sign warning of a "cattle stop" (cattle grid/cattle guard)