Hi there! So you know how we use letters to read and write? Like the letters A, B, C, and so on? Well, a long time ago, there was a group of people called the Romans who spoke a language called Latin. They decided to use some of those letters to make their own writing system.
The Latin alphabet is made up of 26 letters, just like the alphabet we use today. Each letter makes a specific sound when we say it out loud. For example, the letter A makes the sound "aah", the letter B makes the sound "buh", and so on.
Now, Gaj's Latin alphabet is a little different. It was created by a man named Ljudevit Gaj who wanted to make it easier for people who spoke different languages in the same area to read and write. He added some extra letters to the Latin alphabet to represent sounds that aren't used in English. For example, he added the letter Č, pronounced "ch", and Š, pronounced "sh".
So, when people use Gaj's Latin alphabet, they can write words in their own language but still use the same letters as everyone else in the area. It's like having a secret code that only some people know how to read and write!