Having seen one sentence in "Practical English Usage" by M.Swan (a very popular grammar book), I was really puzzled.
I waited until the rain had stopped.
The past perfect is generally used to show that one past action was completed before the other one, but here, trying to analyze the sentence, we can't say that first the rain stopped and then she waited. I can't grasp the use of using the past perfect in this sentence.
Why does this sentence use the past perfect?