The collar design is one of the essential features defining the style of every shirt; the collars of the early shirts were cut in various ways. The fundamental distinction is that between the stand-up collar and the turn down collar.
Some of the collar shapes.
THE WIDE TURN-DOWN COLLAR - The wide turn-down collar is the most formal, and at the same appears the least conspicuous collar style. The gap between the collar tips may vary.
These are also the examples of turn-down collar. I vaguely remembered reading somewhere that Ronald Reagan said, "its possible to make long neck look shorter by wearing a wide collar, just as a short neck can be made to look longer with a narrow collar".
THE CUTAWAY COLLAR - This elegant collar shape has many names, mostly it’s called the cutaway, or the spread collar. The name refers to the typical way in which the collar tips are cutaway to the sides. In fact this design allows a free view of the neck tie knot. The cutaway looks more elegant than the extremely turn-down collar.
THE PIN COLLAR - The pin collar, on which the collar tips are connected with pins of various designs, is also a very American collar style. Sometimes the collar design looks very elegant. The pin collar can be worn with collar tips which are relatively close to each other.
THE BUTTON-DOWN COLLAR - this design has a special stature among collar designs. It looks just as good with a necktie as without. Someone who wears this collar with a necktie look very "dressed up", nevertheless, the button down collar looks less formal than other designs.
THE TAB COLLAR - this design is very famous in USA than in other parts of the world. It was supposedly first worn by Prince of Wales, later Edward VIII on a journey to the USA. Americans adopted this style with enthusiasm. The small strap emphasizes the knot of the necktie very elegantly. However the collar cannot be worn without a necktie.