What is 1812 Overture?
Refers to Pyotr Ilyich Tchaikovsky's "Overture to 1812 in E Flat Major" Op. 49. It is a very famous piece and sometimes said to be one of Tchaikovsky's best works. It is commonly played during the 4th of July because of it's triumph over war sounds.
Listen for 1812 Overture during the 4th of July, you're bound to hear it sometime.