Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Bali to Limerick as you normally would.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Denpasar Bali Ngurah Rai Airport to Shannon Airport flight would often be abbreviated as a DPS to SNN flight. While you’re still figuring out your travel plans, it’s not a bad idea to learn the names and codes of other airports around these areas: Cork Airport (ORK), Knock Intl Airport (NOC), Milltown (Kerry) Kerry Airport (KIR), Galway Airport (GWY), Waterford Airport (WAT).