Sini is a type of script that people use to write things down. It comes from India and is mostly used by people who speak languages like Malayalam and Tamil.
Imagine if you were trying to write a letter to someone but instead of using the letters of the alphabet, you had to use little pictures to represent each word. That's kind of what sini is like! Instead of using letters, it uses tiny pictures called "letters" or "characters" to write words.
Sini is very different from the alphabet that most of us are used to. For example, the letter "a" is just a simple curve in our alphabet. But in sini, there is a character that looks like a little house with a pointed roof that represents the sound "a".
So, when someone writes in sini, they are using a special set of characters to represent sounds and create words. It's kind of like creating your own secret code. And just like with any language, people need to practice and learn sini in order to be able to read and write it.