Scottish Gaelic is a language that people in Scotland used to speak a long, long time ago. It's a language that is very different from English, which is the language that most people in Scotland speak now.
The Scottish Gaelic language is a type of Celtic language. It's kind of like how dogs are different breeds, but they're all still dogs. Scottish Gaelic has its own special alphabet with 18 letters. Some of the letters look like English letters, but they make different sounds.
When Scottish Gaelic was first spoken, there were no books or computers to help people write it down. People passed the language down from generation to generation by telling stories and singing songs. Later, when people did start writing it down, they used a special type of alphabet.
Scottish Gaelic is still spoken in some parts of Scotland, especially in the Highlands and Islands. Some people learn Scottish Gaelic because their parents or grandparents spoke it, while others learn it because they think it's important to keep the language alive.
If you wanted to say "hello" in Scottish Gaelic, you would say "halò." If you wanted to say "thank you," you would say "tapadh leat." See? It's kind of like talking in a secret code!