Article III, §2 of the Constitution limits federal courts to hearing only "cases" and "controversies." Through case law, the Court has interpreted this limit to mean that the courts may hear only those disputes which are traditionally thought to be resolvable through the judicial process — in the language of the courts, these cases are "justiciable." Simply put, the case itself can't be brought to court if: a) the court has no way of deciding the case; b) the court can't provide a remedy, even if the case is decided; c) the case isn't an actual right-here-right-now dispute between two parties with real interests involved (as opposed to a hypothetical dispute with no "skin in the game"); or d) the case involves an issue that is already delegated by the Constitution to another branch (i.e., a so-called "political question").
However, even if the case itself is justiciable, the person bringing that case must have "standing." The idea behind "standing" is that independent of whether a dispute exists that a court can remedy, the person raising the dispute must have the legal right to be in front of the court in the first place.
The plaintiff gains this right by meeting a three-pronged test: First, the plaintiff must have suffered an "injury in fact," i.e., "an invasion of a legally-protected interest which is (a) concrete and particularized, and (b) actual or imminent, not 'conjectural' or 'hypothetical'"; second, a causal connection must exist between the injury and the conduct complained of, that is, "the injury has to be fairly . . . trace[able] to the challenged action of the defendant, and not . . . th[e] result [of] the independent action of some third party not before the court"; and third, "it must be 'likely,' as opposed to merely 'speculative,' that the injury will be 'redressed by a favorable decision.'" (all quotes from Lujan v. Defenders of Wildlife, citations omitted)