Okay kiddo, do you know what a keyboard is? It's the thing we use to type on a computer. We press the buttons (called keys) to make letters, numbers, and symbols appear on the screen.
Now, in Tamil language, they have a different set of letters and symbols than what we use in English. So, they have a special keyboard made just for them! It has all the Tamil letters and symbols on the keys.
When someone wants to type in Tamil on the computer, they switch the keyboard to the Tamil mode. Then, they can press the keys to make Tamil letters and symbols appear on the screen.
It's kind of like having two sets of keys for the same piano. One set is for playing English songs and the other is for playing Tamil songs. We just have to switch between them to play the right tune!