Syntactically, the dollar sign itself means nothing -- to the interpreter, it's just another character, like
q. But a lot of people using jQuery and other similar frameworks will prefix variables that contain a jQuery object with a $ so that they are easily identified, and thus not mixed up with things like integers or strings. You could just as easily adopt the same convention by prefixing such variables with
jq_ and it would have the same effect.
In effect, it is a crude sort of Hungarian notation.