The translation for "communion lists" is:
- Kommunion in Swedish
- Entoollisella kàyneet in Finnish.
Communion is the taking of the sacrament of the Lord's Supper. In some Scandinavian countries and for some time periods, ministers would make name lists of those whom they'd served the sacrament to on any given Sunday. Normally, the entries would read, "Eric Persson and wife, mother, daughter" or "Olof Olsson's widow." Finding such an entry would help you establish the a person was in a certain place at a certain date, which is sometimes very necessary but would not provide much more information.
If there has been a loss of records or if you desire background information, searching communion lists might be helpful. However, they are not the first or most feasible record source to search for life event information on your Scandinavian ancestors.
In Sweden and Finland, for some parishes and time periods, the communion lists were recorded as if they were a census, where all family members were listed by name and sometimes age. This was not country-wide, however.