Colemak is a different way to organize the letters on a keyboard so you can type in a way that's faster and easier. It's like changing the order of the letters in a book so you can read more quickly and understand better.
Normally, we use a keyboard called QWERTY which was made by someone a long time ago. QWERTY has the letters arranged in a way that was supposed to be good for typing on a typewriter a long time ago, but it's not always the best for typing on a computer today.
Colemak, on the other hand, is a newer way of arranging the letters. It's designed to make typing faster and more comfortable by putting the most commonly used keys in easier-to-reach places.
For example, QWERTY has the letter "A" on the left side of the keyboard, but Colemak puts it in a different spot that's easier to reach with your fingers. Colemak also puts the letters that are used most often in the home row, which means you don't have to move your fingers as much.
Overall, Colemak is just a different way of typing that some people find makes them faster and more comfortable. It's not necessarily better or worse than QWERTY, it's just different.