In general the first interview is a more open conversation, discovery over the phone followed by another interview either onsite or on the phone, focused more on skill set, experience etc. The 3th interview is most likely onsite or video if needed having a particular tast, a role play or a recruitment strategy for a particular role that is shared with you a couple of days before hand to have time to prepare. The last meeting can be with your manager especially if he is not based in Dublin. It is more of a final, confirmation chat.