Can a iphone 5s work in ierland?

I'm thinking of getting a iphone 5s but i'm moving to Ireland in a few months (south) so i'm wondering if it will work but with a new sim or something?

It'll work but if you move to a different country you'll probably have to switch to a new carrier. I don't think IPhones have a sim? I'm not sure but if you want to save all your data you can back it up on iCloud.