American Sign Language, or ASL, is its own language.
It is not just a gestural form of American English
It has its own set of rules to govern how it is used
Its own symbols, syntax, pragmatics, etc.
For example, in spoken English, the symbol for a four legged animal that says “Meow” is “cat” however the symbol for this same thing in ASL is the sign for “cat”. You can completely communicate in ASL without ever speaking a word.
This is a language that does not use speech.