It's roughly as I expected.
The baron primarily holds three kinds of rights: land ownership, military power, and economic power.
These three major rights encompass many things.
To put it simply.
Land ownership means the power to collect various taxes within one's territory, including land tax, poll tax, trade tax, etc.
They also have the power to allocate, and even life-and-death decision over, the peasants within their territory.
The second right, military power, allows the baron to establish his own Knight Order and soldiers, forming his own armed force. Of course, the expenses come out of their own pocket.
As for the third, economic power, this includes trade monopolies, such as in salt and iron industries. They can control the production and sale of goods, obtaining substantial profits.
There are also some political rights, such as participating in the council when the King convenes it.
Of course, it must be some of the more important barons.
