What's the difference between : and ; ? how and when do i use them in sentences? give clear examples !

Semicolon - ;

Is used when you need to piece two sentences together but using a comma wouldn't fit or be appropriate for the sentence. As follows:

"I have to study for finals tonight; I can't go out."

Colon -  :

Is used for "As follows" ect.

Example: <-- (That)

Primary colors:   <-- (That)

Red

Blue

Yellow

Good luck!

greet them:

buenas noches.

that is considered night time which is when "good night" is used.