Well as simply as I can:
A empire is a collection of kingdoms.
A kingdom is a collection of duchies.
A duchy is a collection of counties (usually 2-4).
County is the lowest title you can have, but it can also contain bishoprics, castles, towns.
Vassals work up the chain in reverse order usually, so the holder of the town will be vassal to the county holder, the county holder to the Duke, then the Duke to the king etc.
These are de-jure titles but at the earlier start a lot of Duke titles don't exist. If you own more than 50% of the counties in a dukedom you can make the Duke title for a price if it doesn't exist.
A empire is a collection of kingdoms.
A kingdom is a collection of duchies.
A duchy is a collection of counties (usually 2-4).
County is the lowest title you can have, but it can also contain bishoprics, castles, towns.
Vassals work up the chain in reverse order usually, so the holder of the town will be vassal to the county holder, the county holder to the Duke, then the Duke to the king etc.
These are de-jure titles but at the earlier start a lot of Duke titles don't exist. If you own more than 50% of the counties in a dukedom you can make the Duke title for a price if it doesn't exist.