Once upon a time, a long, long time ago in England, there were many kings who ruled over different parts of the land. But then came a time when some of these kings became very powerful and started ruling over more than one area. These powerful kings were called bretwaldas.
Think of it like a game of schoolyard kings, where each kid had their own little kingdom. Sometimes one kid gets really popular and starts to tell the other kids what to do, and pretty soon all the kids are listening to them and following their rules. That kid would be like a bretwalda.
The word 'Bretwalda' comes from two Old English words. 'Bret' meant 'Britain', which is the name for the island that England, Scotland, and Wales are on. 'Walda' meant 'ruler'. So put them together and bretwalda was a ruler of Britain.
To become a bretwalda, a king had to be very strong and powerful. He had to be able to defeat other kings, conquer their land, and get them to accept him as their leader. This way, he could control a larger part of the country than just his own little kingdom.
Being a bretwalda was a big deal because it gave the king a lot of power over the other kings in the area. He could make them pay him taxes or tribute, and he could make them go to war with other kingdoms if he wanted to. So, it was a very important title to hold, and the kings who were bretwaldas are remembered in history for a very long time.