I understand this means hairdressing? so my questions are: i have seen a few of these razors on the bay and various places, what the differance between this sort of straight, and a normal straight, and can you use them to shave?
Ah, hmm...
Coiffeur is actually French for barber.
Straight razors have been used to cut/style hair for almost as long as they've been used for shaving. Originally the same razor was used for both purposes. This type of razor cutting worked best with thick, straight hair.
Over time some barbers/stylists discovered that narrower moustache/trimming type razors gave them more control and flexibility in cutting and styling finer, longer hair.
Then came the hair shaper which may have been designed independently of, or evolved from, the clip-on safety guard for straight razors. The toothed guard allowed for easier thinning/layering of hair.
In 1958 Edmond Roffler invented the Roffler method of razor cutting hair, drawing inspiration from various existing methods and utilizing a narrow blade. It's now the most popular method of razor cutting hair since it is a consistent method that can be taught to anyone.
Razor cuts for hair are still popular today. Many barbers who give razor cuts use the same straights that they use for shaving customers.
To answer your question, it depends on the razor. Some straights that are marked coiffeur are normal straights that are targeted to the stylist market through labeling (see Kentos' post above). Just like some vintage straights were labeled "For Barber's Use". They're just regular straights and almost always hollow ground since those work best for hair cutting.
Some are very narrow (3/8, etc.) for use with the Roffler method or its forerunners. You could still technically shave with them.
Some are meant to be used with a guard like Durhams and Wecks. You could technically shave with them but it probably wouldn't be that comfortable.
Pedantic busturd!
So what is a coif? Too lazy to google...Head? No tete is head.