What is American English?
English is a language which originated in England and is spoken in Britain and other countries. Some countries speak what is called a variety of English, using slighly different vocabulary, pronunciation and, sometimes, grammar.
In the USA, people speak a variety of English called American English or, more accurately, US English. The differences are mainly in spelling (colour/color), vocabulary (lift/elevator) and accent.
Other varieties of English include Australian English and Canadian English.