The first option is the correct explanation:
Sign language is any system of communication using visual gestures and signs, whereas ASL (American Sign Language) is a specific visual language used by Deaf people in the United States and parts of Canada that uses handshape, movement, and facial expression to convey meaning.
In essence, sign language can refer to any variety of signed languages used by Deaf communities worldwide, while ASL is a specific language with its own grammar, vocabulary, and cultural context.