Equal parts flour, butter, hot pan, make your roux (not browned, just enough to cook the flour taste out), add milk. Just like white breakfast gravy but no meat flavors.
Right on target. There are three types, normally mentioned. Thin, medium, thick. You get these by the amount of milk added to the base of butter and flour.
I like to season with a little salt (not much), black pepper (or white Pepper, depending on the final outcome wanted) and a little fresh grated Nutmeg. Lately, I have been substituting ground Mahleb for the Nutmeg.
Bechemel is of course, just one of the 5 French "mother" sauces. Mastery of these 5 will make you one up on most cooks.
Allemande, Bechemel, Veloute, Tomato and Espagnole. Heck, even of those, 4 out of 5 start with a roux. It's not complicated, but it is very interesting. And Tasty.