Answer 1

Simply put, character encoding is how to represent (encode) a character with a sequence of bytes. For ascii letters (uppercase and lowercase without accent) or numbers this is standard for all (reasonable) encoding. But special characters (such as à, Ô, or €) may be encoded in different ways.
UTF-8 is a fairly standard encoding which has been adopted as default for HTML 5. Other common encodings include Windows-1252 (also known as CP-1252) and ISO-8859-1.