Hi,
selector is an ID or class of the element that is used as condition, this is atuo set by cck to the id of selected element, this option is here for those that need to change that for some reason, so if you don't know why you would need it, I suggest not to change it
Attributes are form element attributes, if put in a,b,c and their values and you look at the source you will see e..g. <option a="sth" b="sth else" c ="sth else 2">, this can be also used to set some custom attribute need e.g. for jquery validation like validation="validate"
This element are meant for developers to be able to customize cck default behaviours, there are no premade quick recepies (you might be able to find some on the forum)