A marching band is a group in which instrumental musicians perform while marching, often for entertainment or competition. Instrumentation typically includes brass, woodwind, and percussion instruments. Most marching bands wear a uniform, often of a military style, that includes an associated school or organization's colors, name or symbol. Most high school marching bands, and some college marching bands, are accompanied by a color guard, a group of performers who add a visual interpretation to the music through the use of props, most often flags and rifles.

Many bands have auxiliaries that add a visual component to the performance. For ceremonial bands, this could be a traditional color guard or honor guard. For drum & bugle corps and corps-style field bands, this could include Dance lines, majorettes, Auxiliary units may be collectively referred to as color guard or visual ensemble.  Auxiliaries may perform as independent groups. In the early 1970s, color guards began to hold their own competitions in the winter (after the American football season, and before the beginning of the summer drum and bugle corps season). These became known as winter guard. There are also numerous dance competitions in the off-season.  The color guard of a marching band or drum and bugle corps may contain sabers, mock rifles, and tall flags. In modern bands, other props are often used: flags of all sizes, horizontal banners, vertical banners, streamers, pom-poms, even tires, balls, and hula hoops or custom built props. The color guard may also employ stage dressing such as backdrops, portable flats, or other structures. These can be used simply as static scenery or moved to emphasize block drill, and are often used to create a "backstage" area to store equipment and hide personnel.  While military color guards were typically male, band color guards tend to be primarily female, though it is becoming more common for men to join as well. A few independent units are all-male. Guard members nearly always wear a special uniform or costume that is distinctive from that of the band, not necessarily matching in design or color. The men's and women's guard uniforms are usually designed in one of two ways: nearly identically, but with gender-specific parts (i.e. skirts) adapted for the use of the opposite sex; or complimentarily, with the two uniforms designed similarly but with variations in color or form. The color guard uniform, especially in a high school marching band, need not be in school colors; in fact, they rarely are. These uniforms are designed to represent a certain aspect of the halftime show, characterize the guard members through costumes, or tell some sort of story, and can thus be in any design or color (a surprisingly common complaint among the high school audience is that guard uniforms and equipment "aren't school colors").  Indoor color guards have become popular within high schools and universities throughout the United States. These groups perform a theme-based show in competitions after the outdoor marching band season ends. Indoor color guard shows are typically performed in school gymnasiums and are adjudicated.

Do they compete any other time of the year?
after the American football season, and before the beginning of the summer drum and bugle corps season