AngularJS: infinite scroll with ng-repeater

Question

i am new in angular. so hopping many site to read nice article on angular code example. so today i visited a site http://www.dotnetawesome.com/2016/03/infinite-scroll-for-facebook-like-pagination-angularjs.html

which come with a example like how to create infinite scroll with angularJS.

here i will post some question which is not clear to me. so please answer and guide about those syntax and code in the article because i need to understand.

1) there is one function called NextPage() which the function name has been assign with directive name like this way

<div infinityscroll="NextPage()" style="height:400px; overflow:auto;"> ?

$scope.NextPage = function () {
if ($scope.CurrentPage < $scope.TotalPage) {
$scope.CurrentPage += 1;
GetEmployeeData($scope.CurrentPage);
}
}

tell me what does it mean to assign function name with directive name

<div infinityscroll="NextPage()" style="height:400px; overflow:auto;"> ?

does it mean when directive will load then the NextPage() function will be called or it has different meaning ?

2) see the directive code first

app.directive('infinityscroll', function () {
return {
restrict: 'A',
link: function (scope, element, attrs) {
element.bind('scroll', function () {
if ((element[0].scrollTop + element[0].offsetHeight) == element[0].scrollHeight) {
//scroll reach to end
scope.$apply(attrs.infinityscroll)
}
});
}
}
});

what is the meaning of this line scope.$apply(attrs.infinityscroll)

hence i am new so i am fumbling when reading article on angular js v1+. so please answer my 2 questions in details to guide me. thanks