Cryptids are animals or beings thought to exist by certain people, but not generally accepted. They include urban legends. An Urban Legend is defined as:

"A modern story of obscure origin and with little or no supporting evidence that spreads spontaneously in varying forms and often has elements of humor, moralizing, or horror." -Dictionary.com

Cryptids are common legends spread though-out the modern world. Cryptids are not myths, as they are more modern and have current origins. An example of an urban legend would be a Poltergiest, meanwhile a mythical creature would be a Cyclops.