Shops, gyms and hairdressers are among retailers re-opening on Tuesday morning, as level five COVID-19 restrictions are lifted.
The re-openings are taking place with strict adherence to protective measures, and face coverings must be worn.
People are still being advised to work from home and not to mix with other households outside of those within their support bubble.
People should also stay in their county apart from work, education, medical and other essential purposes.
This restriction is due to be eased on December 18th.
However in outdoor settings, away from a home or garden, up to six people from a maximum of two households can meet while maintaining strict physical distancing.
The number of guests who can attend weddings is 25, irrespective of venue, while couples resident in a particular county - but with existing plans to get married - can travel to get married outside that county.
Places of worship, such as churches, are also allowed to re-open for services for a maximum of 50 people.
Face coverings should be worn in these settings.
There is also a recommendation to wear a face mask outdoors on busy streets.
Museums and galleries can also open from Tuesday with protective measures in place.
While from Friday, restaurants and pubs serving food can welcome customers back.
This can be done for indoor dining with additional restrictions, including a requirement for meals to be prepared on site, with a maximum of six people per table.
This includes access for non-residents to restaurants in hotels.
Gardaí will be maintaining checkpoints nationwide as part of the move to level three.
Over 100 checkpoints will be in place daily on Ireland's main routes, with the support of additional mobile checkpoints.
Static checkpoints will operate during off-peak hours - from 10.00am to 4.00pm and 7.00pm to 9.00pm.
While fixed checkpoints on motorway/dual carriageway routes will no longer be in place.
But there will be high visibility patrols in key city, urban and retail locations in the run-up to Christmas.
There will also be patrols that will focus on the night-time economy.
Gardaí say will be liaising closely with retail and licensed premises.
Garda Commissioner Drew Harris said: "Throughout the pandemic there has been very good compliance by the public with the health advice and regulations. It is critical that this continues in level three.
"While people are able to undertake more activities and travel wider from December 1st, we all need to remember that COVID-19 is still with us and we should act accordingly.
"We all must continue to play our part by heeding the public health advice. This is the best way of protecting ourselves, our loved ones and our neighbours."
Nursing home visits
One person a week will be allowed to visit a nursing home resident through level three and four restrictions.
This is subject to a risk assessment in each case.
Under level five, the rule would change to one person every two weeks.
Nursing Homes Ireland says new guidance on visits to nursing homes are a positive development for both families and residents.
It will take effect from December 7th and replaces window visits.