Male underwear is worn under clothes so as to protect the genitals from friction, to provide support, and to keep clothes clean. While t-shirts and tank tops are also underwear, or at least started as underwear, this article deals solely with below-the-waist underwear.
While loincloths have been worn since ancient times, underwear as we know it today came into existence as a result of the invention of knitting machines around 1800.
According to Wikipedia, underwear first appeared in an advertisement in 1910. Boxer shorts, much easier to manufacture, are older than briefs. The jockstrap, which antedates the brief, first appeared in 1874 to provide support for riders of the newly-invented bicycle.
Once they became available, middle class boys wore "tighty whities", white briefs, a slang term that emerged in the 1980s, when boys’ underwear in colors began to appear. Today (2015), though surprisingly there is no vendor specializing in them, printed cotton briefs are available in a variety of boyish themes: race cars, superheroes, athletes, etc.
Boxers were and remain more common among young blacks. They invented the phenomenon known as "sagging", deliberately wearing pants so low that some, or much, or all of the underwear is visible. (See http://sagger.tumblr.com.) Pants are sometimes attached to the legs rather than the waist, so the entirety of the underwear is visible. This style is commonly said to be a result of the young black man's prison experience - not universal, but far more common than for young white men, and in some communities a normal and expected part of the lifestyle (spending time in prison). Clothes issued in prison typically do not fit properly, though open pants sagging is not accepted by prison guards.
Until the 1970’s, almost all male underwear was utilitarian and white. Since the sexual revolution of the late twentieth century, male underwear became available in colors, then became inventive in styles and fabrics. Today (2015) there is much more variety in men's underwear than in women's, and several Web sites specialize in sexy or revealing male underwear, while long-time female underwear and fuckwear specialist Frederick's of Hollywood has filed for bankruptcy.
Pictures of boys in underwear
Pictures of clothed boys are legal everywhere, with the exception that some jurisdictions criminalize possession of photos that focus preferentially on the genital area (see Dost test). Pictures of naked boys are of questionable legality, as the Azov Films Prosecutions show.
Pictures of boys in underwear are apparently legal in the U.S. At least, an underwear company, Tiger Underwear Store, openly posts its archive of catalogs showing boys in underwear in seductive poses, or boys with underwear peeking over their pants' waistbands. The company on its Web site offers a slide show of their pictures of boys in underwear.
Commerce in used underwear
A well-developed trade in used female underwear exists. In Japan there are stores ("burusera") that specialize in it; unsurprisingly, considering Japanese men's fascination with schoolgirls (Japan was the last country where child pornography was legal), the underwear of minor girls is preferred, although it has gone semi-underground since the government has tried to prohibit it. Used underwear was at one point sold in vending machines on subway platforms.
Clean used underwear is not what men want or buy. Because of its contact with the genitals, underwear picks up smells and stains, and this is what men want: the dirtier the underwear, the higher the price. Purchasers smell it while masturbating. Some men swap their wives' scented panties.
Although much less developed (the market is smaller), used men's underwear is also for sale.
The sale of used children's underwear is legal, although clandestine, and allows the purchaser to do by proxy what cannot be done legally in person: smelling the child's smells. A news story reveals that a man was paying a mother $2000 a month for a supply of her daughter's underwear, and she introduced him to five other mothers doing the same. Dads smelling their own daughters' panties is not unusual (put "dad smells panties" in a search engine).
Panties (knickers in England) are by definition female underwear. However, men also wear them for fetishistic reasons, or sometimes for comfort. The practice is growing and becoming increasingly open and unashamed since 2000, at least in Western countries. Stores that sell women's underwear are increasingly comfortable with male patrons. While some women are uncomfortable with it, others think it's a hoot (fun), or sexually stimulating for them as well. While there is a well-developed community of male pantywearers (see http://www.hewearspanties.net), and occasionally there will be a picture of a leatherman with panties, as something super-kinky, the gay male community remains in general still devoted to the hypermasculine. Many more straight men than gay men wear panties.
Boys have started wearing panties too. In some cases these are gender-variant boys, who feel somewhat, or completely, feminine, and wear dresses and other female clothing as often and as publicly as they can. Other boys wear panties for the same reasons men do: they've seen pictures of men in panties on the Internet (usually masturbating) and find it a "hot", sexy thing to do. Some parents are comfortable with it - the dad may wear them too.
Lingerie for kids
Starting in 2010 articles appeared in newspapers decrying (of course) the marketing of lingerie to children, specifically in sizes for young girls (4-12 years old). The French line Jours après lunes makes identical lingerie in women's and girls' sizes, so mom and daughter can dress alike. Crotchless panties for girls are also available. While these products are taken as evidence of the alleged moral decline and (unwelcome) sexualization and "pornification" of American society, the lingerie remains available (2015), meaning that parents are buying it for their children. Girls' Lingerie is a category on some Web sites that sell girls' clothes. Lingerie specifically for boys (as lingerie is made for men, see http://hommemystere.com) has not yet appeared.
- Tom Burns, "Why I Bought Boy's Underwear For My Daughter", Huffington Post, January 22, 2013, http://www.huffingtonpost.com/2013/01/22/buying-boys-underwear-for-my-daughter_n_2526847.html.
- Anne Jungen, "Child porn, girls' underwear seized in Holmen as part of international investigation", LaCrosse (Wisconsin) Tribune, May 6, 2015, http://lacrossetribune.com/news/local/child-porn-girls-underwear-seized-in-holmen-as-part-of/article_1260f43b-fd2b-505c-aeec-26d6537d9e85.html.
- Hope Alexander, "While I Like My Men to Wear Lingerie," November 15, 2010, http://hopealexander.hubpages.com/hub/Men-In-Panties-Why-I-Like-My-Men-In-Lingerie.
- Dhani Mau, "New French Lingerie Line Jours Après Lunes is for Girls Four through 12--Cute or Crossing the Line?", Fashionista, August 15, 2011, http://fashionista.com/2011/08/new-french-lingerie-line-jours-apres-lunes-is-for-girls-ages-four-through-12-does-it-cross-the-line
- "Crotchless Panties Sold At 'Kids N Teen' Store Upsets Colorado Parent", Huffington Post, November 15, 2011, http://www.huffingtonpost.com/2011/11/15/crotchless-panties-kids-store_n_1095184.html