A group of people on the bark, brightly lighten street, while one man with a gray hat holds a large colorful sign with arrows.
The people are walking down the street.
People are on the street. People tend to walk when they are on the street. The second sentence is a simplification of the first.
Sentence 2 explains what the people are doing. A group of people on a street with signs is likely a protest march, which usually involves people walking down a street.
People walking down the street and the street maybe well lit and may have other attributes to it.