Cognizable offence basically means that offence under Indian criminal law for which a police officer may arrest without a warrant.

Bailable offence is an offence under the first schedule of the Criminal Procedure Code (CrPC) or bailable by other laws for which bail can obtained.

Non-bailable offences like murder, crime and conspiracy against the state etc are those offences specified for which even the Courts cannot grant bail.

'Complaint' means any allegation, made orally or in written to a Magistrate with a view to his taking action under the CrPC that some person, known or unknown, has committed an offence but it does not include a police report.

Section 155, CrPC
When information is given to an officer in charge of a police station of the commission of a non-cognisable offence, he shall enter the substance of the complaint in the station diary any other official record book of the police station.

No police officer is empowered to investigate a non-cognisable offence without the order of a Magistrate having power to try such a case and commit to trial;

Any police officer can action an NC except in relation to arrest without warrant;

If there is no more than one criminal offences involved in the complaint and of them is cognizable, the whole case will be treated as cognisable.