The red and white on the Polish flag are the national colors of Poland. The use of these colors on the flag dates back to 1831 when the colors were officially adopted. However, they have been used as national colors of Poland since the Piast dynasty.
Before 1831, soldiers in the Polish army wore various colors and types of cockades. There was a desire to make this practice more uniform, so the colors of red and white were adopted.
The main Polish flag features two equally sized horizontal bands, the top one white and the bottom one red. But there is a variation to this flag. It has the same two bands, but the top white band also features the image of a crowned white eagle on a red background. This eagle is the coat of arms of the Republic of Poland.
This variation of the flag is used as a civil and state ensign. It is also commonly used in place of the main national flag, including by the Polish diaspora. This includes many living in the United States. Polish flag day is celebrated on May 2 each year. In addition to this, all the symbols of the country, including the flag and the crowned white eagle coat of arms, are celebrated the following day, May 3, as part of Poland's Constitution Day.