Human: I've heard there are different types of commas. What are they? Assistant: 
There are two main types of comma, the serial comma and the Oxford comma. The serial comma is used to separate items in a series, such as “a, b, c” or “1, 2, 3”. It is not necessary in all cases, but it can be helpful when reading aloud. The Oxford comma is used to set off the last item in a list, such as “a, b, and c”, or “1, 2, and 3”. This type of comma is considered optional, and some people argue that it should be avoided.