What does the '+' mean in front of phone numbers? We visited the British Isles lately and saw numbers listed like: +353 51 305555
This shows that there's a country code added to it.
For example here we have a 10 digit telephone number starting with 01 to 05 (5 big regions in the country), 06 or 09 means it's a cellphone...
But if you were to try and phone us from another country you'd need to start with the country code: +33, the first 0 pops out so that a phone number would look like +33
I don't think it was like that a few years ago but now when I receive a call, even from inside my own country, there's always the country code at the front, my phone even tells me what country it's from in the call log (but not while it's ringing), usefull to avoid scam calls from other countries!
+353 is Ireland, they probably add it to be sure people traveling will be connected to the right number regardless of where they are (maybe there's some spots or cellphones who pick up the UK network instead of the Irish one even if on Irish land? Or if they're in Northen Ireland maybe?)
ETA: it's also pretty usefull for tourists, that way they don't even have to think and look for the area code,