New words are always being added to the English language. Sometimes a new word is simply invented, but there are many other ways for words to enter the language.
1) An existing word can take on a new meaning.
The word 'web' already existed before the invention of the world wide web.
2) The name of the inventor or producer of an item can be used as the name of the item itself.
The ball point pen was invented by a Hungarian man, Laszlo Biro, and ball point pens are now referred to simply as 'biros'.
3) A noun can be used as a verb and vice versa.
To 'microwave' something means to cook it in a microwave oven.
4) A word can be formed by combining existing words.
A shopaholic is someone who is addicted to shopping. The word comes from shopping + alcoholic. (An alcoholic is someone who is addicted to alcholic drinks.)