(You might want to read the description of "nothing" after you have already read the descriptions of the other hand rankings.)
What can you say about "nothing"? If you don't have any higher ranking hand, then you have "nothing". The cards below represent a hand that would rank as "nothing":
It isn't a "Pair", it isn't "Two Pair", it isn't "Three of a Kind", it isn't a "Straight", it isn't a "Flush", it isn't a "Full House", it isn't "Four of a Kind", it isn't a "Straight Flush", so what is it? Nothing.
There is an episode of The Simpsons where one of the characters tries to convince Homer that even though Homer is holding a "nothing" poker hand, he has actually won the game -- so he calls Homer's hand a "Royal Sampler". Funny stuff.