Yh, that question ^^^
Generally a prime minister is the leader of a parimentary form of goverment. He is not selected directly by the people. He is the leader of the political party that controls the parliment. A president is usually selected directly by the people in a democracy, or in our case though an electoral college that is based on each states people voting for that candidate.
jimahl's analysis is correct. The only thing I would add is that a prime minister often has many of the executive powers a president does. And since he's in parliament and elected by the parliament, the executive and legislative branches are joined together. This means there is very little check or balance to what the government does.