Need to understand IN, SELECT, VALUE, FROM, in Entity Framework

Working on this EF tutorial, I've difficult to understand the meaning of the following markups

<asp:EntityDataSource ID="CoursesEntityDataSou开发者_如何学Gorce" runat="server" 
                  ...

 Where="@PersonID IN (SELECT VALUE instructor.PersonID FROM it.People AS instructor)">
                  ... 
</asp:EntityDataSource>

So what's this, pure SQL or Linq 2 Entity?

For what I understand,

1. it.people is people object that comes out of the query
2. FROM and AS makes sense in a pure SQL point of view

Taken together, they don't really make sense to me, and the tutorial didn't give much information.

Thanks for helping

This is another part of Entity Framework called Object Services. It allows you to perform the same object queries but without using LINQ to Entities. Generally it's used when you want to stream query results in DataReaders or in very limited scenarios where LINQ to Entities can't give you what you need.