or, to translate
The origins of Cockney Rhyming Slang are uncertain. It's not really a language since the words spoken are clearly English; on the other hand, it's not a dialect either, since the speakers of this slang are also perfectly capable of not using it! Some stories go that this slang originated in the market place so that the vendor's could communicate without the customers knowing what was being said - you wouldn't want your customers knowing that you were going to lower your prices in ten minutes so you could go home early. Other stories have it that it originated in the prisons so that inmates could talk without the guards listening in. It doesn't really matter where it comes from - the important thing is that it exists today just as it has for many, many years and can provide a wonderful, colourful language in everyday life.
It is very difficult to describe what Rhyming Slang is without using an example, but I'll give it a try. Basically, you take a pair of associated words (e.g. fish hook), where the second word rhymes with the word you intend to say, then use the first word of the associated pair to indicate the word you originally intended to say. Usually. And some slang words have more than one meaning (for example, iron can be a bank (Iron Tank) or a homosexual (Iron Hoof - this rhymes with poof which is a particularly English expression for homosexuals), so context is everything! There - clear as mud.
Let's use an example: From the example listed above, you are talking about a book. The rhyme is "fish hook", so the slang expression is fish, as in "I'd like to say a word about the new fish by Len Deighton" except, of course, a real Cockney would more likely say "I've got a dickie about Deighton's new fish"; dickie is from dickie bird (i.e. word). Doesn't really clear things up at all, does it? Imagine a conversation like this:
which really means,
Now you've got an idea about what is possible, why not go back to the previous page and try your hand at it!