If you are an EU/EEA citizen, you have the right to work, study, or live in Sweden without a residence permit. The right of EU/EEA citizens to stay in Sweden without a residence permit is called right of residence. You have right of residence in Sweden if you are employed, self-employed, a student, or have sufficient means to support yourself.
If you are a citizen of Denmark, Finland, Norway, or Iceland, you may be considered both a Nordic citizen and an EU/EEA citizen, and you can therefore use two different sets of rules if you want to live in Sweden.
If you are a Swiss citizen, you can move to Sweden to for example work or study, if you want to stay in Sweden for longer than 90 days, you require a residence permit.