If you listen to native speakers, you may hear words that you can not find in a dictionary. The use of informal words and expressions is also called slang. Slang is sometimes regionally used or by a particular group like teenagers, musicians, members of a minority,...
Some of the words change their meaning, for example the words hot or wicked.

In East London, the Cockney rhyming slang can be found. Unfortunately, there are only very few people who can really speak it. The principle is to find a word which rhymes with the word you want to say. For example:

phone          bone                        I talk on the bone.

believe         Adam and Eve         I don't Adam and Eve it!