以下是我从Google上找到的一个例子，非常生动形象，我修改了部分代码，具体内容如下：
对于$root 与$parent的区别：
- $root refers to the view model applied to the DOM with ko.applyBindings;
译：$root 是指ViewModel所应用于ko.applyBindings时所使用的DOM;
- $parent refers to the immediate outer scope;
译：$parent 是指当前DOM元素直接的外部父类（只有一层）;
Or, visually, from $data's perspective:
Or, in words of the relevant documentation:
- $parent: This is the view model object in the parent context, the one immeditely outside the current context.
- $root: This is the main view model object in the root context, i.e., the topmost parent context. It’s usually the object that was passed to ko.applyBindings. It is equivalent to $parents[$parents.length - 1].
对于三者的区别（$root，$parent及$data）：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title></title>
<script type="text/javascript" src="knockout-3.4.0.js"></script>
<style>
th, td {
padding: 10px;
border: 1px solid gray;
}
</style>
<script type="text/javascript">
window.onload = function () {
vm.mainPerson(grandpa);
grandpa.children.push(daddy);
daddy.children.push(son1);
daddy.children.push(son2);
ko.applyBindings(vm);
}
var Person = function (name) {
var self = this;
self.name = ko.observable(name);
self.children = ko.observableArray([]);
}
var ViewModel = function () {
var self = this;
self.name = 'root view model';
self.mainPerson = ko.observable();
}
var vm;
vm= new ViewModel(),
grandpa = new Person('grandpa'),
daddy = new Person('daddy'),
son1 = new Person('marc'),
son2 = new Person('john');
</script>
<script type="text/html" id="person">
<tr>
<td data-bind="text: $root.name"></td>
<td data-bind="text: $parent.name"></td>
<td data-bind="text: $data.name"></td>
</tr>
<!-- ko template: { name: 'person', foreach: children } --><!-- /ko -->
</script>
<table>
<tr>
<th>$root</th>
<th>$parent</th>
<th>$data</th>
</tr>
<!-- ko template: { name: 'person', data: mainPerson } --><!-- /ko -->
</table>
</head>
<body>
</body>
</html>
具体页面呈现：
The $root is always the same. The $parent is different, depending on how deeply nested you are.
译：$root经常是相同的，而$parent是不同的，而这种不同主要取决于你嵌套的深度。