Buckles can be distinguished both by their purpose and by the material they're made from. Some buckles are primarily functional, while others serve a decorative purpose.

Functional buckles are adjustable attachments that link two ends of a belt together or attach two straps. Because buckles are adjustable, they can be used to tighten or loosen an opening, as with a belt or the carrying straps on a backpack, or a closure can be secured, as with the straps on a satchel. They can also be used on straps to hold something in place securely.

Buckles are commonly used with items that we attach to our bodies: watches, belts, fanny packs, and backpack straps all characteristically have buckles, often made of metal or plastic, depending on the function and strength needed. Buckles of this kind are also found on riding saddles. Buckles used to close items include those for satchels, handbags, and knapsacks. Buckles used to help keep things in a particular place include those found on automobile and airplane safety belts, stroller and car seat straps, and straps found inside some pieces of travel luggage.

Ornamental buckles are widely available for belts and a popular item of Western clothing, specialty clothing that grew out of ranch and cowboy culture. Ornamental buckles may also be considered jewelry. Western buckles may include precious stones, precious metals such as gold and silver, or rhinestone decoration. Popular themes for Western buckles include abstract designs, scenes or objects from ranch life, or a word or initial. Commonly found are longhorn steer, horses, patriotically themed images, and words like cowgirl or cowboy up.

A specialty group is Native American belt buckles. Hopi, Zuni Pueblo, Navajo, and other Southwestern Indian jewelers are among those whose work in this area is widely known, and they often work in silver, turquoise, and sometimes beadwork. Artisan buckles are not limited to Western and Southwestern themes, however, and individual jewelers work in silver, legal ivory, mother of pearl, and a wide variety of gems, as well as pearls. One can also find antique buckles including Art Deco, Art Nouveau, and cloisonné pieces for belts, shoes, and capes, both available for sale and on display in museums.