Difference between postdoc and researcher in Sweden? At Uppsala universitet there are currently open positions as mathematics postdoc and as researchers. The announcement texts are identical, aside from this part (and clarification on it) that is missing from the researcher position:


  To be eligible for a position as postdoctoral researcher the applicant's PhD degree must have been obtained no more than three years prior to the application date; however, for example periods of sick leave or parental leave are deducted from the three-year period.


What is the difference between researcher and postdoc in the Swedish system in general, or Uppsala university in specific?
The difference is that a postdoc's PhD degree must have been obtained no more than three years prior to the application date.  For a researcher, there is no such limitation.

It means they want a postdoc, but if it's been more than three years, they can't call her/him a postdoc and will call her/him a researcher.  They'll probably pay more for the researcher but they probably would also pay someone with 8 years of postdoc experience more than someone with 2, even if they were allowed to call both a postdoc (like they would in, for example, the UK).

It's common in Sweden.  See this question.