American Sign Language is a language using hand and body gestures that was created to help Deaf and hard of hearing people in America communicate their thoughts and feelings. American Sign language is considered a separate language and culture from the language and culture of spoken English. Sign language has variations, and people outside of America may not understand ASL, even if they are Deaf and/or fluent in their own sign language.
ASLMeredith has a series of themed videos teaching ASL.
Bill Vicars has hundreds of ASL lessons on YouTube and on his website.