In deciphering what type of door lock you have, the first indicator to look at would be the material of the door.
If you have a wooden door, you are likely to have one of two lock options. The first lock type that you might have would be a mortice lock, otherwise known as a deadlock, which can usually be found around waist height on the door. The key is often flag-shaped and the lock itself is particularly safe as the only way to gain entry is to use destructive methods, such as drilling. Wooden doors may also have a rim cylinder fitted, which has a jagged edge to the key and is often found around shoulder height. When a rim cylinder is fitted, it is often accompanied by a night latch, found on the inside of the wooden door. This allows for extra security as the nib can be pushed down and for the door to be opened from the inside.
Wooden doors can be incredibly safe if they have both a rim cylinder and a 5 Lever British Standard Insurance Approved Mortice Lock.
You may find that you have, or would like to have, additional security features fitted to your door. Improving the security of a wooden door could include adding a door chain and a spy hole.
UPVC and Composite Doors
UPVC or plastic doors will usually have a euro cylinder (the part in which the key enters and turns) accompanied by a multipoint locking system, otherwise known as the mechanism. When the UPVC door handle is pulled up, it engages the mechanism that runs along the inside of the door. This, as the name would suggest, locks the door at multiple points, providing a much higher level of security.
Additional security can be added by installing Sash Jammers to the inside of UPVC doors and windows, making it harder for burglars to enter. You can also upgrade to an anti-snapping lock. You can find more details about updating to premium security locks here.