There are lots of similarities between joinery and carpentry, which leads many to believe that they are both one and the same occupation. This couldn’t be farther from the truth.
Yes, carpenters and joiners both work with wood, and yes both can become site managers as a result of their skills, but many experts draw the line between both occupations when it comes to scope.
Joinery is much more specialized in scope than carpentry. For example, while joiners work exclusively with wood, carpenters can in fact go beyond this and work with metals.
Joiners used wood alone to create fixtures and fittings in doors, furniture and so on, but a carpenter tends to make use of metal objects such as screws and nails to install their features in place.
This, I believe, is the most important distinction. You can learn more about the specialized function of a joiner here.