Ephemera is usually considered to be two-dimensional material printed on paper, although there can be exceptions. For example, bookmarks might be printed on silk, celluloid, or other materials and still qualify. Items such as campaign pin-back buttons, Scout badges and pins, and packaging cartons evade the two-dimensional definition but are usually accepted as ephemera.

In addition, the transitory nature of ephemera varies. Some items are meant to be used once and discarded, such as tickets, advertising flyers, postage stamps, and newspapers. Some ephemera is intended to be kept for a limited time, including magazines, catalogs, calendars, receipts, manuals, instructional booklets, and postcards. Other items are actually produced to be kept and treasured - memorial cards, souvenirs, literary keepsakes, photographs, and items printed with collecting interests in mind, such as trading cards.

There are hundreds of categories of ephemera, including letters, photos, diaries, match book covers, brochures, seed packets, luggage tags, menus, posters, maps, prints, greeting cards, stocks and bonds, ledgers, broadsides, Victorian trade cards, political and military memorabilia, timetables, deeds, popcorn bags, historical documents, laundry lists, business cards, and so on.

Why do people collect this stuff? The reasons for collecting ephemera are as numerous as the categories of the material itself. Some love the artistry. Many fine illustrators created postcards, trade cards, magazine covers and ads, posters, and other illustrated items. Other pieces represent the epitome of design styles, such as Art Nouveau, Art Deco, or Art Moderne.

For some, these little paper treasures reveal the history of printing or advertising techniques. Early currencies, stocks and bonds, and other pieces of business paper often demonstrate the highest standards of the engraver's art. One collector has used crate and can labels to detail the history of United States Pacific Coast lithographers, as well as the agricultural history of the area.

Many industries now avidly purchase items related to their business to create or enhance company archives. Individuals trace the history of cultural developments such as agricultural tools, veterinary practice, quack medicine, forms of transportation, racial and political issues, and historical events through acquisitions of newspapers, magazines, letters, documents, catalogs, advertising, and other forms of ephemera. What may seem like whimsy to the uninitiated may, in fact, be part of important historical research. On the other hand, whimsy is just as compelling a reason to collect some ephemera.

Collectors define their own parameters. One person may collect Victorian trade cards, the next only cards having to do with cosmetics, the next with cosmetics cards having to do with soap, and yet another only Fairy Soap cards. Some will pursue anything with their name on it - either a first name, a family name, or items from a family business. (We are always in search of advertising, postcards, and photos that feature Kirk's Bakery or Kirk's Kandy Kitchen, businesses owned by my husband's grandparents in Rhinelander, Wisconsin.)