Okay kiddo, so Madhava was a very smart man who lived a long time ago in India. He loved math and he came up with a way to make doing math easier.
One thing he did was make something called a sine table. Now, sine is a math word that has to do with triangles and circles. Madhava figured out that if you know the size of a circle, you can figure out something called the sine.
So Madhava made a big chart that had all the sines for different angles. It was really helpful for people who did math because they didn't have to figure out the sines each time they did a problem. They could just look it up on Madhava's table!
That's why Madhava's sine table was so important, because it made math easier for lots of people.