Short answers, pulled from the story.
Serfdom began to develop in the 3rd century AD when large landowners relied on tenant farmers known as coloni due to a severe labor shortage. The condition of these tenants eroded over time because Emperor Diocletian implemented a tax system assessed based on both land and its inhabitants.
Unlike slaves, serfs could not be bought, sold, or traded individually but could sometimes be sold together with the land they occupied. Actual slaves such as kholops in Russia had no rights over their own bodies and could leave the land only if freed, whereas serfs received protection and justice in return for working the lord's fields.
Labor requirements in Poland rose significantly over centuries until six days per week per household became common by the 18th century. Serfs worked on the lord's demesne fields, mines, forests, and roads while spending the remainder of their time tending their own crops and animals.
Reforms by Jacques Necker abolished serfdom in all Crown lands in France in 1779. Although formal serfdom no longer existed in most of France by that date, feudal seigneurial laws still granted noble landlords many rights previously exercised over serfs.
Russia's over 23 million privately held serfs were freed from their lords by an edict of Alexander II in 1861. State serfs were emancipated four years later in 1866 following this major legislative change.