Punctuation is the use of spacing, conventional signs, and certain typographical devices as aids to the understanding and correct reading of handwritten and printed text, whether read silently or aloud. (Encyclopedia Britannica)  Another description is: “The practice, action, or system of inserting points or other small marks into texts, in order to aid interpretation; division of text into sentences, clauses, etc., by means of such marks” (Oxford English Dictionary).

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

• .  is a period or full stop
  •    ,  is a comma
  •    ?  is a question mark
  •    !  is an exclamation mark
  •    ‘  is an apostrophe
  •    ”  is a quotation mark/inverted comma
  •    :  is a colon
  •    ;  is a semicolon
  •    …  is an ellipsis
  •    –  is a hyphen
  •    –  is a n-dash
  •    —  is an m-dash

Reasons for punctuation (https://simple.wikipedia.org/wiki/Punctuation#Rules_of_punctuation  )

One reason is obedience. If we work for an organization with a house style guide, then we use that guide.

Punctuation helps the reader understand what is meant. Consider these examples:
1.) He did not go to town because his father was absent. This means he did go to town, and the reason was not his father’s absence.
2.) He did not go to town, because his father was absent. This means he did not go to town, and the reason for not going was that his father was absent.

In the second example, no style guide will help. The writer just has to make sure that the sentence is understood as it is written. Punctuation is there to help the reader make sense of what is written. Often it is best to change the sentence so that the meaning does not rest on a comma.

1.) He went to town, but not because his father was away.
2.) Because his father was away, he did not go to town.
That seems to make the meanings clear.