The flag that is white on both sides and has a blue strip in the middle and another white strip next to each side is called a white-blue-white flag. It looks like three stripes, one blue in the middle and two white stripes next to it.
This type of flag is used for many different things, like on boats to show that they come from a specific country or organization. It might also be used on military vehicles, uniforms or buildings to show that they are part of a particular group or belong to a certain country.
Sometimes a particular pattern of flag might be used to show support for something or someone, like when people wave flags at a sports event to cheer for their favorite team or athlete.
Overall, the white-blue-white flag is just a way to show who you are or where you come from, and it can be used in many different ways.