What is the difference between cream cheese and sour cream?
There are differences in base ingredients, as well as in the method used for production. The production of cream cheese starts with milk (or a mixture of milk and cream), which is curdled after which the whey is removed. Typically, rennet or acid are used to curdle the milk, so that one can separate the whey from the curds. Cream cheese can be fermented before curdling, but I do not believe this is common.
Sour cream is cream that has been fermented with lactic acid bacteria.
The difference in names is thus also explained: sour cream is cream that has gone sour, while cream cheese has undergone a fairly typical cheese-making process.