All of these are one in the same. Straight razors are a single edge blade that can be most commonly associated with a fold-able knife. The best razors are made with variation of surgical grade stainless steels. These razors will provide the closest shaving experience but do require some experience and finesse when in use. The advantage of a straight razor is that you groom the blade after each use with a strop thereby negating the need to buy razors entirely. With proper care and maintenance, these razors can, and have been known to be passed down for generations.