Probable cause means that a "reasonable person" would believe that a specific person was in the process of committing, had committed, or was going commit a crime.
Probable cause is enough for a police officer to ask a judge for a search warrant or arrest warrant. It is also enough for a police officer to make an arrest if he or she sees a crime being committed.
What is reasonable suspicion?
Reasonable suspicion requires the officer to have specific facts, not just a hunch, that a person is involved in a crime. If an officer has reasonable suspicion, he is able to briefly stop a person to ask questions to confirm or refute his suspicion.
If an officer approaches you, ask if you are free to leave. If you are free to leave, calmly walk away.
If you are not free to leave, the officer may ask you for your name or ID. In Arizona, you must give the officer your name or ID so the officer can identify you.
You do not need to answer other questions about what you are doing, where you are going, or why you do not want to talk to the officer.
Your refusal to answer questions is not evidence of your involvement in a crime.
If an officer stops you, he or she may frisk – or patdown – you for weapons if the officer has reasonable suspicion to believe you are armed and dangerous.
If the officer, during the pat down, can tell by touch alone that the item he is feeling is illegal, he can remove the object.
 Terry v. Ohio, 392 U.S. 1, 21 (1968); see, e.g. In Re Roy L., 197Ariz. 441, 444-45 (App. 2000).  A.R.S. 13-2412; A.R.S. 28-1595.  Floridav. Bostick, 501 U.S. 429, 437 (1991).  Statev. Serna, 235 Ariz. 270, 271 (2014).  Minnesotav. Dickerson, 508 U.S. 366, 372 (1993).