If you would like to work in Ireland and are not a citizen of the EU or European Economic Area, then you will need to apply for a work visa. There are four main types of employment permits: General Employment Permit (formerly Work Permit), Critical Skills Employment Permit (formerly Green Card), Dependent/Partner/Spouse Employment Permit, and Reactivation Permit.
There are also five more that are more specific, but which may apply to your circumstances. Ireland also has a Working Holiday Visa programme for a few reciprocal nationalities.
EU and European Economic Area citizens