Answer by taking a quote from the following article:

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.

Traditional Style bands, also known as Show Bands, are marching bands geared primarily towards crowd entertainment and perform on football fields. Typically, they perform a routine before the game, another at halftime, and sometimes after the game as well. Competitive show bands perform only one show that is continually refined throughout a season, while bands that focus on entertainment rather than competition usually perform a unique show for each game. These shows normally consists of three to five musical pieces accompanied by formations rooted in origin from Patterns in Motion, a book penned by band director William C. "Bill" Moffit, bandmaster of Purdue University All-American Marching Band and University of Houston Spirit of Houston.  A recognizable style of show band is the one fielded by historically black colleges and universities (HBCUs). HBCU bands utilize the traditional "ankle-knee" high step and music selections are largely based on R&B, hip-hop, and contemporary popular music. In addition to traditional drill formations, HBCU bands feature heavily choreographed dance routines as part of their performances. Many of these bands may have a twirler line and/or a dancer line, but not necessarily flag twirlers. One of the most notable depictions of HBCU bands is the film Drumline. HBCU bands are a significant part of African-American musical culture and HBCU bands often surpass their associated football teams in popularity, a phenomenon that is uncommon among collegiate and high school marching bands. In 1989, as part of the celebrations for the bicentennial of the French Revolution, the Florida A&M University Marching 100, one of the most prolific HBCU bands in the country, was selected as the official representative of the United States in the bicentennial parade.  Another style of show band is that used by many of the Big Ten Conference marching bands, a semi-military and semi-corps style. These bands perform a show that is designed to entertain the audience, but feature more traditional symphonic styles of music (marches, film scores, jazz, or older pop music) as well as some contemporary music. Big Ten style show bands have been influential in creating some of the earliest marching band innovations, and the style is used in high schools throughout much of the United States.  Most show bands of either type include the traditional military band instrumentation of woodwinds, brass, and battery percussion. Some also include the front ensemble keyboard percussion, and may also incorporate the use of a color guard for flag, and rifle routines as well as a dance line.

What do they try
while bands that focus on entertainment rather than competition usually perform a unique show for each game.