What LINQ and LINQ syntax is this tutorial?

Hi, sorry I am new to LINQ. 

May I know which LINQ type and syntax is this tutorial? I will wanna to study more on that type of LINQ first so that I can understand the tutorial better. Thanks

https://docs.microsoft.com/en-us/aspnet/web-forms/overview/getting-started/getting-started-with-aspnet-45-web-forms/display_data_items_and_details