An exclamation mark is placed at the end of a sentence that expresses:
Ouch! You trod on my toe.
Oi! Get out of my garden.
In direct speech to indicate that the speaker is shouting:
“Look out!” shouted dad as he dropped the hammer.
”Get down from there!” yelled the teacher when he saw the boys climbing the tree.
When the writer finds something amusing:
When the clown appeared at the party all the children burst out crying!
There has, lately, been a trend in informal wnting to place multiple exclamation marks in writing, especially in social media.
Presumably this is to emphasise how strongly the writer feels about a particular topic. (…!!!). However, in formal writing this is generally regarded as bad form, as is combining a question mark with a question mark (…!?)