There is no easy way to determine when clothing was first developed, but some information has been inferred by studying lice. The body louse specifically lives in clothing, and diverged from head lice about 107,000 years ago, suggesting that clothing existed at that time. Another theory is that modern humans are the only survivors of several species of primates who may have worn clothes and that clothing may have been used as long ago as 650 thousand years ago.Additional louse-based estimates put the introduction of clothing at around 42,000–72,000 BP.Other evidence suggests that humans may have begun wearing clothing as far back as 100,000 to 500,000 years ago.
Physically, clothing serves many purposes: it can serve as protection from the elements, and can enhance safety during hazardous activities such as hiking and cooking. It protects the wearer from rough surfaces, rash-causing plants, insect bites, splinters, thorns and prickles by providing a barrier between the skin and the environment. Clothes can insulate against cold or hot conditions. Further, they can provide a hygienic barrier, keeping infectious and toxic materials away from the body.

Clothing also provides protection from harmful UV radiation. The most obvious function of clothing is to improve the comfort of the wearer, by protecting the wearer from the elements. In hot climates, clothing provides protection from sunburn or wind damage, while in cold climates its thermal insulation properties are generally more important. Shelter usually reduces the functional need for clothing. For example, coats, hats, gloves, and other superficial layers are normally removed when entering a warm home, particularly if one is residing or sleeping there. Similarly, clothing has seasonal and regional aspects, so that thinner materials and fewer layers of clothing are generally worn in warmer seasons and regions than in colder ones.

Clothing performs a range of social and cultural functions, such as individual, occupational and sexual differentiation, and social status. In many societies, norms about clothing reflect standards of modesty, religion, gender, and social status. Clothing may also function as a form of adornment and an expression of personal taste or style.

Clothing can and has in history been made from a very wide variety of materials. Materials have ranged from leather and furs, to woven materials, to elaborate and exotic natural and synthetic fabrics. Not all body coverings are regarded as clothing. Articles carried rather than worn, worn on a single part of the body and easily removed, worn purely for adornment (jewelry), or those that serve a function other than protection, are normally considered accessories rather than clothing, as are footwear and hats.

Clothing protects against many things that might injure the uncovered human body. Clothes protect people from the elements, including rain, snow, wind, and other weather, as well as from the sun. However, clothing that is too sheer, thin, small, tight, etc., offers less protection. Clothes also reduce risk during activities such as work or sport. Some clothing protects from specific environmental hazards, such as insects, noxious chemicals, weather, weapons, and contact with abrasive substances. Conversely, clothing may protect the environment from the clothing wearer, as with doctors wearing medical scrubs.