There are 13 stripes on the U.S. flag and they represent the original 13 colonies that signed the Declaration of Independence on July 4, 1776. They were actually admitted as states about 12 years later when they each ratified the Constitution.
Since then a star was added for each additional state that was admitted into the union. The last two were Alaska and Hawaii, admitted in 1959, bringing the present total to 50 states. So our flag presently has 50 stars in addition to the 13 stripes.