What is the difference between $ and jQuery

Question

When I try to use $(\"#div_id\") in $(document).ready it returns NULL, but when I use jQuery(\"#div_id\") it returns the actual object

Answer 1

See jQuery.noConflict(). Could other javascript libraries on your page be using the $ variable?

$ is just a variable that is used to alias jQuery and being a variable, anything could be assigned to it.