Dublin is in the Republic of Ireland (aka Eire) which is a distinct country from the United Kingdom of Great Britain and Northern Ireland (aka Ulster).
There are deep religious differences that have simmered and many times boiled over for many centuries which have led to this current political divide in the geographical island of Ireland. If now living there it is advisable to get at least a basic grasp of the situation then and now so as to avoid causing offence. Rule 1 for any of us non-Irish is to not claim to understand it.
