What is brightness?

Brightness is how bright something looks to your eyes.

Imagine you're holding a flashlight. When it's on full power, the light is very bright, like when you shine it in someone’s face. But if you turn it down, the light becomes softer and less bright, like when you use it to read a book at night.

Now think about a lamp. A small nightlight has low brightness, it's just enough to see by. But a big, shiny desk lamp has high brightness, it fills up the whole room with light.

You can also compare brightness to your favorite toys. A tiny glowing cube might not be as bright as a huge, flashing robot. The bigger and more light it gives off, the higher its brightness.

So when you see something that's really bright, like the sun or a flashlight in your hand, it’s because it sends out a lot of light, and that makes everything around it look brighter too!