Feudalism encompasses a range of Social Hierarchies and Government. It usually consists of smaller, weaker lands being ruled by a noble which then pleads their loyalty, some taxes, and levies in the event of war, to a more powerful sovereign above them. The sovereign above them again then owes their subject protection from outside invasion. These arrangements often lie across many layers, with for example the mayors of cities serving barons, barons serving the count, the count serving a duke, and a duke serving the king. Feudalism encompasses an ideology that values values order through tradition and law, many following the law of a Divine Magic order or that of the Concordats, which creates hierarchical structures in which loyalty and responsibility are intertwined.
These titles are usually originally given out to trusted aides and knights of great conquerors or unifiers, and even based on the merit of those capable of running a land - but over time tend to become inherited through lineage. Most who end up in charge of a land namely end up handing out their lands to trusted family and friends, friends’ families might get integrated through marriages forming an alliance, and then one usually raises ones children to become the next ideal rulers.
Archduchies are a type of duchy held by certain duchies that reach a large size, comparable to a kingdom, but which for some reason or other don’t claim the moniker of Kingdom or King.
Empires and emperors are usually something special proclaimed only by those who have a great impact on the trajectory of world history - or those cocky enough to claim they do/will. Rarely, empires and emperors might have kings sworn as their subjects underneath - though more typically emperors tend to also hold kingdom titles directly.
Viceroyalties, handed out to viceroys, is the responsibility for a feudal title given to a person that isn’t meant to be inherited - and which returns to the sovereign who handed it out on the viceroy’s death or abdication. Governorships are similar but of a more permanent nature. Both of these often can turn into inherited realms.
Tributaries are a type of subject that pays tribute, a payment in terms of money and gifts, to their overlord, in exchange for some form of protection - but which otherwise remains a realm running their own matters. Empires may turn smaller realms in lands they don’t care much about as much into tributaries.