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
Citizens from the EU and the European Economic Area do not need any visas or work permits to live and work in Ireland. No job offer or work contract is needed prior to arrival in Ireland, however after the first three months you will either need a job or proof of enough funds to support yourself and any dependents.
EU countries are those that are members of the Euro