You can research for free using "guest" (no quotes) for both the user name and the password. You can see individuals but you can't see the contact information of the researchers.
If you join (about $22 a year), you can see individuals and you can see the contact information of individuals.
If you join and also submit a GEDCOM file of a certain size, you can see family groupings and the contact information of subscribers. Your information will be in the database and others can see it and they can see your contact information.
The subscribers are probably related in some degree. It is important to contact them to share information. They most likely have more information that what is shown in the online database.
This article is old and the percentage of Swedish ancestors included in the database has grown greatly.