Question

I would like to know what $.each() stands for in jquery,
What is it selecting?

Is there an equivalent in prototype?

Answer 1

$.each() isn’t selecting anything. It is just a utility to iterate over a collection.

When you do:

$('someSelector').each(function() {
    // do something
});

jQuery is internally calling:

jQuery.each( this, callback, args );

…with this representing the matched set.

http://github.com/jquery/jquery/blob/master/src/core.js#L231

You could just as easily call it yourself manually.

jQuery.each( $('someSelector'), function() {
    // do something
});