The Fourth Amendment protects you against unreasonable searches and seizures. If the police want to search your house without your consent, they need a warrant. Warrants may only be issued upon a showing of probable cause, supported by an affidavit. The facts contained in the affidavit must do more than support a mere suspicion. The requirement of probable cause for the issuance of warrants is one of your most precious constitutional protections.
Consent dispenses with the necessity of probable cause.
While lacking probable cause, if the police conduct a search with your consent and seize evidence for use against you in court, your lawyer will not be able to suppress it on the basis that the search was warrantless. The Fifth Amendment protects you against giving evidence against yourself, i.e. , your right to remain silent. Just as you cannot be compelled to testify against yourself in a criminal trial, neither can you be compelled to answer a policeman's questions about that AR-15 you bought a couple of years ago and never surrendered. Don't be bashful about invoking this right. It's always better to remain silent and appear guilty than to open your mouth and prove it.