Those are linq expressions. They are indeed wonderful. You get an abstract tree from which you can create SQL or API commands to access the data source. I remember in the early days (.NET 3.5?) there were multiple examples of LINQ2X like Linq2Csv, Linq2Rss Linq2Drobox (I'm paraphrasing, I don't remember actual examples, but it was wild).

There is also relinq library which transforms linq expressions into expressions which are easier to understand/use.