In a nation of laws, there must be courts to adjudicate upon those laws. Yet the courts themselves are governed by laws.
Subject matter jurisdiction
The state courts are courts of general jurisdiction, and may hear cases about any subject matter.
The federal district courts are Constitutionally prohibited (by the Tenth Amendment in conjunction with Article III) from hearing any case that does not fall into one of two categories. First, the district courts have diversity jurisdiction over a case in which no plaintiff resides in the same state as any defendant, and in which it is claimed (at least somewhat reasonably) that the amount in controversy exceeds $75,000. The amount-in-controversy requirement is statutory, not Constitutional. Second, the district courts have federal-question jurisdiction over any case arising out of the Constitution or federal law. (The Supreme Court has also held that the district courts may maintain jurisdiction over state claims that share a common nucleus of operative fact with the federal claims conferring jurisdiction. This is called supplemental jurisdiction.)
Personal jurisdiction
Under the Due Process Clauses of the Constitution, the Supreme Court has held that a defendant must have minimum contacts with a state before he can be forced to appear before a court there. This is true for both federal and state courts. If the defendant (allegedly) commits his crime or tort in the state, that's good enough. If defendant is a corporation that sells tons of projects to the state, one of which injures plaintiff, that's good enough. There is considerable case law about this difficult minimum contacts issue.
A defendant may agree to personal jurisdiction even if he or she does not have minimum contacts with the state. On the other hand, all court actions in a case in which the court does not have subject matter jurisdiction are void. One more note. In this article I have discussed many Constitutional jurisdictional boundaries. However, Congress is Constitutionally responsible for delineating the boundaries, within the Constitution, of federal court jurisdiction. With few exceptions, Congress has given the federal courts jurisdiction to the fullest extent Constitutionally permissible.