Both terms are linked to one another.  The "colonies" refers to land held in other countries like the British holdings in North America.  For example, Virginia was a colony of the British, as was Pennsylvania and Massachusetts. The "colonists" refers to those people who lived in the colonies.  Colonial powers, like the British, saw the people living in the new world territories as an extension of their own nation, just living abroad.  Within the term "colonists," resided a great implication that the British rules and expectations would not be questioned or debated in any way.  It is here where the term "colonists" receives the most amount of discussion because as time progresses, the "colonists" came to be seen as oppositional to the parent nation, as in the example, England.  And, over the course of the events that led to revolution and the conflict itself, the term "colonists" came to refer to the people who lived in the colonies, that, for the most part, defined themselves as being against the colonial power.