CrPC 133 v/s Section 156(3) - Confused

Koi bataayega to main aaj tak confuse hoon ki CrPC 133 under which case can be registered when FIR is not lodged but there's some cognizable offence reported? Toh agar main ek case dekh rahahu, ismein section 156(3) ka mention hai, lekin CrPC 133 ka bhi mention hai, kya yeh dono sections ek dusre ke bair hain ya iska matlab hai ki FIR lodge toh hai? Magar agar FIR lodge nahi hai to kya yeh CrPC 133 ka hi use hoga? Aur agar police apne discretion se case register karegi, kya yeh bhi CrPC 133 ka hi use ho sakta hai? Main kafi confuse hoon yeha.