The basic rule for using the colon

1. Punctuation Basics:
The Rule of the Colon

2. Using the Colon
The colon joins a main clause with another element, which
may or may not be a complete sentence.
Hilary enjoys two things in life: surfing the internet and reading her
email.
Hilary enjoys two things in life: she likes to surf the internet and she
likes to read her email.
The rule for the colon is simple. Whatever appears to the
left of the colon must be a complete sentence;
whatever appears to the right does not have to be a
complete sentence, but it may be one.