Okay, so a long time ago, before there were big stadiums with professional cricket players, people in England played cricket as a fun hobby with their friends. They called themselves "amateurs" because they didn't get paid to play, and they just did it for the love of the game.
As time went on, there became more and more organized groups of amateur cricket players, and they started playing games against each other in different areas of England. Some of these groups even created their own teams and leagues.
In the late 1800s, there was a group called the Amateur Athletic Club that organized a big cricket competition called the Amateur Championship. This was a really important event for amateur players, and it helped make amateur cricket more structured and serious.
Over the years, many famous English cricketers actually started out as amateurs, and then went on to become professional players. But even today, there are still lots of people who play amateur cricket for fun, just like they did all those years ago.