Search, Seizure and Admissibility

We look at the 4th Amendment. What does the right to privacy mean, and what rights do we have as American citizens to protection from an unreasonable search and seizure? What is the difference between “reasonable” and “unreasonable?” What rights do government actors have, both with and without a warrant? Moreover, how are we to understand what is admissible and what isn’t in a court of law?