Correct use of "Semicolon"

So when I was in the 3rd grade and we were learning a bunch of fun "Grammar" rules like semi colon and commas my track system was "off". I was able to pick up on the commas, but to this day I still don't understand the official use of a "semicolon
A semicolon separates items in a list when the items themselves have internal punctuation.
Here is an example of a semicolon.
Gabrielle likes oranges; cherries; and red, yellow, and green apples.