In the U.S., what does it precisely mean that federal courts have limited jurisdiction? I ask because I'm unsure that they cannot hears cases in which the president or the Congress are involved.
The term "jurisdiction" means "the power to make official legal decisions and judgements". When a court has limited jurisdiction, that court can only hear certain types of cases. For example, a bankruptcy court can normally only hear bankruptcy cases, and thus has limited jurisdiction.
Federal courts have limited jurisdiction in that only certain types of cases can be heard in them:
To determine whether a case can be heard or not (assuming an actual case has been initiated by some party), the following must apply:
There is a very readable article on the US Courts website covering more details about jurisdiction (and was the source for my lists above).