When do you use them?
When a comma just isn't good enough!
Typically a semicolon is used for a discontinuity or pause.
It sits between two independent clauses (sentences that can stand on their own),
without the use of a conjunction (and, but, or).
EX. I have a date tonight; I cannot run errands.
The semicolon brings together two independent clauses that are related.
If you want to learn the fun way, check THIS out!