There are concepts, and there are design options (or versions). They aren’t the same thing. It may seem trivial to point out the differences, but there are countless situations where the 2 have been interchanged, and someone isn’t happy with the work. Knowing when to do which, is important and limits the times you’ll have

A good brief is like directions off a desert island. It should give you the correct information in the absence of your client or your account team. The brief is your guideline, your life-line and your go-to document for all the important stuff. Unless it isn’t a good brief. Well, then you need another set