The British Invasion was a time in the 1960s when lots of British rock bands, like The Beatles and The Rolling Stones, became really popular in America.
Think of it like when your friend brings a really cool toy over to show you, and you like it so much that you want to play with it all the time, and then you tell all your other friends about it, and soon everyone wants one.
It was pretty much the same with the British Invasion; American kids started listening to British music and liked the style and sound so much that it became really popular. Plus, the bands looked really cool in their matching suits and long hair.
The British Invasion changed the music scene in America, and lots of people still listen to the songs from that time period today!