List set queried by LINQ

I always heard my colleagues talk about LINQ and know that I learned it when I went to school. But I have never used it since I graduated. I always think it is a good skill, but when I really learned how to use it, I found that so easy. Let's talk a little bit about code.

VaR list1 = (from F in listfund where F. userid = ID & (f. changetype = 1 | f. changetype = 40) & (f. reasontype = 40 | f. reasontype = 1) Select F. amount ). sum ();

This is a piece of code for querying the list set by using LINQ. In fact, it is similar to SQL statement usage, except that in is followed by a list set. I understand it as traversal. Where is followed by the query condition select followed by the field to be queried, the only difference is the select position.