What does ;(function(global,$,_){ }(app,jQuery,_)); mean?

What does ;(function(global,$,_){ }(app,jQuery,_)); mean?

In one javascript file, the script was wrapped into this, why wrap codes
into this? Any reference to this? Why define Basepage=global.Basepage?
;(function (global,$,_){
var Basepage=global.Basepage = Backbone.View.extend({
});
}(app,jQuery,_));