What does the `shiftBind` function here mean?

In a javascript snippet, I saw codes like this..

nglr.shiftBind = function(_this, _function) {
  return function() {
    var args = [ this ];
    for ( var i = 0; i < arguments.length; i++) {
      args.push(arguments[i]);
    }
    return _function.apply(_this, args);
  };
};

This looks a little abstract for me to understand... Could anyone have an example about what this really does..

Thanks!