Rule 2: The semi-colon is used in a list where there is more description of each item.
We normally use a comma to separate items in a list, e.g. At the circus we saw a clown, a lion, a fire eater and an acrobat.
However, when we describe items more fully, it is best to separate the items with a semi-colon, e.g. At the circus we saw a clown juggling with swords; a lion who stood on a ball; a fire eater with flashing eyes; and an eight year old acrobat.