If you are a Nordic citizen, you may travel freely to Norway without a residence permit. The only thing you need to do is to register in the National Population Register.
If you are an EU/EEA citizen, you are eligible to work in Norway without a residence permit. If you plan on staying longer than 6 months, you need to register your move to Norway with UDI, the Norwegian Directorate of Immigration, within 3 months after your arrival, and book an appointment with the police that you must attend in person.
Non-EU/EEA citizens need to apply for a visa or a resident permit, to be able to work in Norway. A visa will allow you to enter Norway for a specific period of time, whereas a resident permit will give you citizenship for residence on a permanent basis.
Type of residence permit
There are several different permits available. Visit UDI to see which visas and permits apply specifically to you.
If you have completed higher education or vocational training, you will most likely be applying for a residence permit as a skilled worker. In order to obtain this type of permit, you will need to have received a job offer or have your own business.
Skilled workers who have not yet obtained a residence permit, can apply for an entry / visitor visa to visit Norway for up to 90 days.
Some exceptions apply. For instance, if you are an artist or if you are working for an organization that carries out international humanitarian work. In these cases you can stay up to 14 days without a working visa.
There are also separate rules for athletes, continental shelf workers and seafarers. You can read more about visa-free workers here.
For Ukranian asylum seekers, read more information here in English, Ukranian or Russian.