What does the jQuery() function in jQuery do?

Question

In this video there is a snippet of code that goes something like this:

if (jQuery) {jQuery(function() {
    // ...
})}

I\'ve never seen the

Answer 1

I think it is the same that using $() but you use jQuery() for compatibility with other libs which also use $()

jQuery can be a variable that store a function. Guess that if is to check if it is not undefined or something like that