Okay. Firstly, the basics of punctuation.
Commas:
Commas are used to separate adjectives (a word that describes a noun). Separating adjectives with commas means that you have an expanded noun phrase. You can only have 2 or 3 adjectives in an expanded noun phrase. But remember this: don't put commas at the end of sentences!
Full stops:
Full stops are used to close a sentence or statement.
Colons and semi-colons:
Semi colons go instead of the words "and", " but" and "or" while colons go instead of the word "because".
Replies
Colons follow independent clauses (clauses that could stand alone as sentences) and can be used to present an explanation, draw attention to something, or join ideas together.
An example of a descriptive sentence using a colon:
There was only one terrible option for the vile monster: get horrid revenge on his heartless creator.
An example of a colon being used to introduce a list:
Victor quickly grabbed the items he needed: a long, twisty rope to climb high places; a small, but deadly pocket knife incase the vile monster threatened to attack; a tiny bottle containing vicious poison to pour into what the horrid creature would eat.
These sentences are based off the story Frankenstein by Mary Shelley
In addition, semicolons can also be used to join two related independent clauses in place of a comma and a coordinating conjunction (and, but, or, nor, for, so, yet).
For example:
I needed to go for a walk and get some fresh air; also, I needed to buy milk.