Night latches are usually referred to as a ‘Yale’ locks. These types of security automatically lock when the doors close and are generally fitted to wooden doors.  They are normally fitted to the rim of the door, but can come in mortice versions. 

British Standard (BS) Night Latch locks can be fitted if you require more robust security to your property.  BS locks are usually have a  larger case and bolt with a security latch that stops the bolt from being ‘slipped’;