Mostly, in news broadcasts and the like, when there is some political business going on overseas, it will be between parties which can be described with short epithets to give foreigners a broad brush (and probably rather inaccurate) picture of the cut of the jib of the various parties: centre-right, populist-nationalist, socialist, christian democrat, and so on.
Usually, any particular struggle will be between two parties or factions which can be differentiated on that basis. For example, in a centre-right party, a traditionalist conservative wing might fall out with the free-market liberal wing. Or there might be a fight between a socialist party and a capitalist party. And so, on. This at least gives listeners the illusion of understanding the matter at hand.
This seems not to work for understanding the Republic of Ireland. Sinn Féin, The Labour Party and Solidarity-PBP are understandable on this basis, but from the outside the two historically largest parties seem almost impossible to distinguish! Both seem to be centre-to-centre-right christian democratic parties, and they seem to exchange policies and positions at a confusing rate (for an outsider).
I've read a little about the founding of the Republic and the Civil War and I kind of understand where the parties came from historically and how, back in the day, that would have been very important. Also, it seems to me that the Irish Civil War was not so long ago in the memory, and that the wounds from civil wars take a long time to heal.
But how does an Irish person, at the ballot box, inclined to the centre-right, choose between Fianna Fáil and Fine Gael? Is it possible for someone outside to understand? Is it something like tribal loyalty, supporting a team? Or, in complete contrast, is it a matter of who happens to have the better manifesto at each election? Does it reflect class, history, region, etc? Is there actually some difference in traditional left/right (or similar) terms which I've failed to pick up on?