Commas 1

Commas are used for separating describing words, to make the sentence easy to read.

Note: there shouldn't be any comma between the last describing word and the thing it describes.

In 1939 there were dark, ominous, portentous clouds hanging over Europe.

Here is an example that uses two sets of lists within one sentence and separates them with careful use of commas.

Note: This writer does not use the Oxford comma (explained below)

Plato believed that democracy encouraged certain inferior and undesirable character traits in society, namely shallow, egotistical and acquisitive citizens, who justified their selfishness, cowardice, insolence and wastefulness with lexical slipperiness. 

Commas are used to separate list items in a simple list in order to make the sentence easier to read. Note: Often there is no comma between the last two items if you use an and between them, although at times it may be appropriate (The comma when used before the final and is called the serial or 'Oxford' comma. [Discussed in the next section])

Qualities needed to become a top sportsperson include perseverence, confidence, focus(,) and discipline.

The following may be symptoms of pavor nocturnes: confusion, disorientation, panic (,) and dislocation.

The Oxford Comma: AKA the 'serial' comma

Should you include a comma before the final and in a list... or should you not?

It is interesting how flustered some grammar nerds get themselves over it!

Turns out it is a matter of preference between England and the USA, and between style in different contexts such as university publishers and newspaper publishers.
Sometimes it matters (because it changes the meaning), but often it does not matter.

We found this neat lesson from TED-Ed
TED-Ed: The Oxford comma debate. (Opens in a new tab)