Im sure they can explain it a lot better than I can if they’re from the area. In the mean time, I’ll give you my outside perspective based on general knowledge coupled with that of having a few friends in the region.
A lot of tension there, based on a long and complex history and varying degrees of conflict. The flag of Northern Ireland is the flag of the UK. The flag of the Republic of Ireland is Green, White, and orange. Not long ago, a couple decades at most, it was a very tense place with pretty serious and frequent violence. I have friends in the area that say that it’s still a somewhat tense situation today, but as an American I don’t really have much first hand experience of the day to day to go by. The history section of the linked wiki has a pretty good summary of historical events and the like.