Plain and simply, that means I use a comma before 'and' in a list.
This means I'd rather write a sentence this way:
'Rhino horns, orangutan hair, and french fries are all rather delicious.'
instead of eliminating the comma after 'orangutan hair.'
We've all been taught in school that this is wrong, and that it's possible we'll die a gruesome, elephant dropping-related death if we do use it. But personally, I love the serial comma. It's the saviour in a bucket of mud.
Here are the technical bits now. 'and' used between two words can signify a group. If we talk about bread and butter, or the famous fish and chips of England, it's a group -- bread and butter go together (even though you can have it with jam and mayo and what have you). It's a tradition.
So you won't write
'I had milk, bread, butter, and cornflakes for breakfast.'
In this case, you'll group up the bread and butter and write
'I had milk, bread and butter, and cornflakes.'
But that isn't the only reason. It's not just the matter of how confusing
'France, England, Bosnia and Herzegovina'
sounds to the layman. Without the serial comma after 'Bosnia', it's impossible to deduce if someone is writing about today's collective 'Bosnia and Herzegovina' country, or whether they're referring to the pre-World War times, when Bosnia and Herzegovina were two separate provinces.
No, the main power of the comma is in the organisation. The multiple commas in the first few elements prepare us for a list, and getting a cold 'and' with no comma is very heartless.
Now examine the aesthetic value of these two sentences:
The dog ate my homework, shorts, catapult, computer, remote-control and spectacles.
VS
The dog ate my homework, shorts, catapult, computer, remote-control, and spectacles.
Not only does the latter avoid the grouping up of the remote-control and spectacles (they aren't even similar objects), but it also looks more in control of the traumatic situation. (If you disagree, may the heavens help you.)
Commas are not always pleasing to spot, especially in the case of three-line long sentences, where the sentence is so long you lose track, and ultimately, tired, you attempt a slow step-by-step breakdown until you come to terms with its meaning, implications, and sheer cleverness.
But you can't deny that the comma after 'implications' gave you an aesthetic pleasure that can only be brought about once a sentence ends.
The serial comma, ladies and gentlemen, is the hero of the day.
Of course, semicolons are a bit better than commas, but unfortunately there is not much opportunity to use them; they're a slightly complex punctuation.