A colon looks like : and is used to set up anticipation for the second part of a sentence.
I have many New Year’s resolutions: use colons correctly, use semicolons correctly, and lose twenty pounds.
Using a colon adds drama to a sentence as it puts the topic at the end and creates suspense
Ice cream is my only love in this world. (OK)
I only have one love in this world: ice cream. (Surprise!)
How do I use a colon?
Colons should always be used after an independent clause
My favorite hobby is: thinking about grammar. (wrong)
I only have one favorite hobby: thinking about grammar. (correct)
What is a semicolon?
A semicolon looks like ; and is used to connect two independent clauses.
I always have many New Year’s resolutions; I never achieve any of them.
While a colon can connect an independent clause and a dependent clause (I have only one love in this world: ice cream.), a semicolon MUST connect two independent clauses
I have only one love in this world; ice cream. (wrong)
I love ice cream; I could eat it every day. (correct)
Why would you use a semicolon rather than a period?
You can connect two short, related sentences with a semicolon rather than a period if you think they are too choppy to stand on their own or if you want to draw attention to the relationship between them.
I made a cake last week; it tasted awful.
However, you can also use a period or a comma to the same effect.
I made a cake last week. It tasted awful.
I made a cake last week, and it tasted awful.
Basically, semicolons are useful if you want to mix things up.
Fun fact! The colon made its debut in 1550, while the semicolon didn’t roll up until 1644.