Parade

A parade is a large or small group of people who all walk together, usually down a street or road. People who walk in parades are often dressed in costumes, and followed by marching bands, floats or large balloons.
Reasons.
They are often held on holidays or to honor someone. Parades are held for many reasons, but are usually for celebrations of some kind. Days like St Patrick's Day are often celebrated with a parade. 
Military parades.
A military parade is one of the most common parades. It is when soldiers march in public. Usually they are followed by tanks and other military vehicles. Military parades are often held after a battle or war has been won. In China, National Day is now celebrated with large military parades in Beijing every 5th year after 1949. In the United Kingdom, the Queen's Official Birthday (now always on a Saturday) is marked by a military parade every year. In the United States, such military parades are less common but usually held on Veterans Day and Independence Day. 
Famous parades.
One of the most famous parades in the United States is the Macy's Thanksgiving Day parade in New York City. Over 44 million people watch this parade on television each year.