this.initialize.apply(this, arguments)这句话的含义

Question

  function ZoomPic () { this.initialize.apply(this, arguments) } ZoomPic.prototype = { initialize : function (id){} } 看了一些别的资料，还是不是很清楚this.initialize.apply(this, arguments)这句话的含义，还有initialize : function (id)为什么不写成initialize = function (id)