Fashion design differs from costume design due to its core product having a built in obsolescence usually of one to two seasons. A season is defined as either autumn/winter or spring/summer. Fashion design is generally considered to have started in the 19th century.While all articles of clothing from any time period are studied by academics as costume design, only clothing created after 1858 could be considered as fashion design.

Some fashion designers are self-employed and design for individual clients. Other high-fashion designers cater to specialty stores or high-fashion department stores. These designers create original garments, as well as those that follow established fashion trends. Most fashion designers, however, work for apparel manufacturers, creating designs of men’s, women’s, and children’s fashions for the mass market.

There are three main categories of fashion design, although these may be split up into additional, more specific categories:

Haute couture : The type of fashion design which predominated until the 1950s was "made-to-measure" or haute couture, (French for high-fashion). The term made-to-measure may be used for any garment that is created for a specific client. Haute couture, however, is a protected term which can only be officially used by companies that meet certain well-defined standards set by the Chambre Syndicale de la Couture. Nonetheless, many ready-to-wear, and even mass market labels, claim to produce haute couture, when in fact, according to established standards, they do not. A couture garment is made to order for an individual customer, and is usually made from high-quality, expensive fabric, sewn with extreme attention to detail and finish, often using time-consuming, hand-executed techniques. Look and fit take priority over the cost of materials and the time it takes to make.

Ready-to-wear : Ready-to-wear clothes are a cross between haute couture and mass market. They are not made for individual customers, but great care is taken in the choice and cut of the fabric. Clothes are made in small quantities to guarantee exclusivity, so they are rather expensive. Ready-to-wear collections are usually presented by fashion houses each season during a period known as Fashion Week. This takes place on a city-wide basis and occurs twice per year.

Mass market : Currently the fashion industry relies more on mass market sales. The mass market caters for a wide range of customers, producing ready-to-wear clothes in large quantities and standard sizes. Cheap materials, creatively used, produce affordable fashion. Mass market designers generally adapt the trends set by the famous names in fashion. They often wait around a season to make sure a style is going to catch on before producing their own versions of the original look. In order to save money and time, they use cheaper fabrics and simpler production techniques which can easily be done by machine. The end product can therefore be sold much more cheaply.

There are three main ways in which designers can work:

Working freelance: Freelance designers works for themselves. They sell their work to fashion houses, direct to shops, or to clothing manufacturers. The garments bear the buyer's label.

Working in-house: In-house designers are employed full-time by one fashion company. Their designs are the property of that company, and cannot be sold to anyone else.

Own label: Fashion designers often set up their own companies. A lot of designers find this more satisfying than working for someone else, as their designs are sold under their own label.

Most fashion designers today have attended some kind of art school. There are a number of well known fashion design schools worldwide.

Many professional fashion designers start off by specializing in a particular area of fashion. The smaller and the more specific the market, the more likely a company is to get the right look and feel to their clothes. It is also easier to establish oneself in the fashion industry if a company is known for one type of product, rather than several products. Once a fashion company becomes established (that is, has regular buyers and is well-known by both the trade and the public), it may decide to expand into a new area. If the firm has made a name for the clothes it already produces, this helps to sell the new line. It is usually safest for a company to expand into an area similar to the one it already knows. For example, a designer of women's sportswear might expand into men's sportswear.