Colons are a sophisticated punctuation choice that allow you to signal relationships between ideas. A colon suggests that the information following it will support, explain or restate the information that was presented preceding it.

The information following the colon can be

a clause

Girls who are in the permanent custody of their mothers showed lower self esteem : normal social and emotional development results from interaction with both parents (Ellis & Watyer, 1999).
a list of words.

During WW2 Australian women formed four major auxiliary war services : the Women's Royal Australian Navy, the Women's Auxiliary Australian Airforce, the Australian Women's Army Service, and the Australian Women's Land Army.
or even a sentence fragment

There are two options which would alleviate the detrimental effects associated with the split attention effect : reducing the extraneous load on working memory or increasing its processing capacity.

Note that the colon is the only punctuation mark that can introduce a sentence fragment.