Police custody means that an accused stays in the lock-up of a police station or at least in the physical custody of the investigating agency probing the concerned matter. On the other hand, judicial custody implies that the accused is lodged in jail and is under the custody of a magistrate.
Soon after the arrest, an accused can be kept in police custody for up to 24 hours. Beyond that, it is the magistrate who decides whether he/she should stay in police custody or be remanded to judicial custody.
Police custody can be extended for a maximum period of 15 days. Judicial custody can be extended to a maximum period of 90 days for offences punishable with more than 10 years of imprisonment, and 60 days for all other offences.