Both are jQuery functions which helps to loop over object list(json, array) in javascript.
map() helps to loop over object list and also helps to return new array.
each() helps only to loop over object list.
Secondly you can break iteration in each() but it won't happen in map().
var items = [1,2,3,4];
$.each(items, function() {
alert('this is ' + this);
});
var newItems = $.map(items, function(i) {
return i + 1;
});
Output: [2,3,4,5]