There are 50 white stars in the blue square. It has red and white stripes. There are 13 stripes.
The 50 stars on the flag represent the 50 states of the United States of America and the 13 stripes represent the thirteen British colonies that declared independence from the Kingdom of Great Britain and became the first states in the Union.
The design of the flag has been modified 26 times officially, since 1777. The 48-star flag was in effect for 47 years until the 49-star version became official on July 4, 1959. The 50-star flag was ordered by President Eisenhower on August 21, 1959.
There are political movements supporting statehood in Puerto Rico (by the New Progressive Party of Puerto Rico) and the District of Columbia, among other areas. A 51st state will require a new design to accommodate the additional star.