On semicolons (from a teacher of university English composition classes):

1. They are used, properly, to separate two units of prose that could stand alone as independent sentences, but are closely-enough related to be connected within a single-sentence structure.

2. They are not strictly necessary. You can separate the two independent portions with a period, and let them stand as single sentences.

3. A comma is NOT a proper or acceptable substitute for a semicolon, and vice-versa.

4. If you are uncomfortable with, or uncertain about the proper use of a semicolon, don't use one. Just make independent stand-alone sentences.

5. Don't overuse the semicolon. It is the habañero pepper of punctuation marks to many people (including editors, whom I will bunch with the larger category of people for the purpose of this comment). Too many will definitely make the dish unpalatable.