Delaware, Maryland and Pennsylvania were proprietary colonies. What was a proprietary colony?

It was the territory and its resources, granted by the British Crown to a person, a rich family or commercial companies, to establish a settlement there for profit.

Explanation:

The "proprietary colonies" unlike the "royal colonies" were not companies established under the direct authority of the crown. On the contrary, they were under the authority of individuals or private groups that had the responsibility of guaranteeing different things. First, the investment of the shareholders. Second, they not only had to pay taxes to the king but also, they had to defend the crown's rights on those territories were there any threats made by other crowns.

In general it was a very inefficient system, since the owners often did not even visit or knew the territories that were granted to them. This was the main reason why at the beginning of the 18th century almost all the colonies had passed into the direct domain of the British Crown, and their status at that time became that of "royal colonies."