It's nearly indistinguishable from a passport, not a national ID card (at least as implemented in other EU states).
The closest thing in Ireland was the "mandatory but not compulsory" Public Services Card and the related MyGovID, until it was ruled unlawful to require a PSC for access to government services.
There really is nothing like a mandatory national ID card in Ireland.
However there’s a passport card, which is nearly indistinguishable from an identity card:
https://en.wikipedia.org/wiki/Irish_passport#Passport_Card