Terry Vs. Ohio (1968), gave light to the term "frisk". A "frisk" is a brief yet cautions examination that involves patting down your clothes. The aim is to find weapons on you. An officer can frisk you in situations where there is reasonable suspicion that you may be carrying a weapon. For example, if you have been stopped and you meet a profile (say, you are wearing clothing that may be concealing a weapon and you happen to be in a place where weapons are commonplace) the officer has the right to frisk you. It is actually not only for the finding of a probable cause for arrest, but also for the safety and security of the police officer.
The "search" is way more thorough than the "frisk" because, if a police officer is granted permission to obtain a search warrant, it means that there is evidence that links to a probable cause that you are connected to a crime (or that you may become involved in a crime in the near future). While after a frisk you may be released, a search may involve your detention, arrest, and then the search will take place. In cases when you may be suspicious of carrying drugs, a search may even involve a body cavity search for which officers are more than fully allowed to do.
Hence, the search is much more thorough and involves a permission to be conducted whereas the frisk can happen at the minimal suspicion of you carrying a concealed weapon.