Sweden proper, Swedish: Egentliga Sverige, is a term used to distinguish those territories that were fully integrated into the Kingdom of Sweden, as opposed to the dominions and possessions of, or states in union with, Sweden.
Specifically this means that from 1353 up to the Treaty of Fredrikshamn in 1809, Sweden proper did also include the present-day Republic of Finland as a fully interated part of the realm, Österland. After 1809 however the use of the term has been to distinguish the western part from former eastern half of the realm, or Sweden from Finland.
The Skåneland, formerly a part of Denmark, came under the Swedish Crown by the Treaty of Roskilde in 1658, but it was not until 1719 that it was fully integrated and became part of Sweden proper.
Only the estates of the realm of Sweden proper, represented in the Riksdag of the Estates. In Sweden this included the fourth estate, the Peasants.
Sweden proper is, as opposed to Finland Proper, a geographical reference that has changed over time, whereas the latter is a province in southwestern Finland that gave its name to all of Finland.