How many types of Client Object model extension are available in 2010 and when would you use one or the other.

To develop rich client side solutions, three set of client-side APIs has been introduced in the Microsoft.SharePoint.Client namespace. The three APIs are targeted for three different types of clients.
1. .net Managed applications – These are used when we have to create console applications or window applications, web applications which are not running inside SharePoint Contex.
2. For Silverlight applications
3. ECMAScript – It is a client object model extension for using with JavaScript or JScript. This is used for creating applications which are hosted inside SharePoint. For example, web part deployed in SharePoint site can use this JavaScript API for accessing SharePoint from browser using JavaScript.