What is the exclusionary rule?

It's the remedy that gives the Fourth Amendment practical effect. Without it, an unlawful search would violate a right with no consequence attached.

The rule reaches beyond the directly seized item. Evidence derived from an unlawful search — statements, additional evidence found as a result, sometimes identifications — can also be excluded under what's called the fruit of the poisonous tree doctrine.

It has significant limits. Good faith can preserve evidence where officers reasonably relied on a warrant later found defective, or on binding precedent later overruled. That last point is doing real work in Florida's cannabis cases right now. Inevitable discovery applies where the evidence would have been found anyway through lawful means. Attenuation applies where the connection between the violation and the evidence is sufficiently remote.

So a violation doesn't guarantee exclusion. It opens the question.