Ulster Irish is a type of Irish language that people in the northern part of Ireland speak. You know how you can speak English, but people in other countries might speak a different language like Spanish or French? Well, some people in Northern Ireland speak Irish instead of English.
Ulster Irish has its own special way of saying words and talking to someone. It uses letters that aren't in the English alphabet, like the letter "ch" which makes a different sound than it does in English. For example, instead of saying "hi," in Ulster Irish you would say "Dia dhuit," which means "hello" in Irish.
There used to be a lot more people in Northern Ireland that spoke Ulster Irish a long time ago. But as time passed, less people learned how to speak it because English became more popular. There are still some people that speak Ulster Irish today, and they want to keep the language alive for future generations to learn and enjoy.