An oval cylinder has an oval shape and is used in conjunction with an oval mortice lock case. A euro cylinder is similar only it is shaped like an enlarged key hole and used in conjunction with a euro mortice lock case. The cylinder fits through your door, passing through the lock case which is mortised into the edge of the door. When using door handles with these types of locks and cylinders, you must ensure that they too have the oval or euro cut out on the back plate to allow the cylinder to pass through.
Yes there are different types as well as different sizes available. They can be supplied as "double key" which allows you to lock the door from both sides by use of a key, or as "key and turn" which allows you to lock the door with a key from one side and with a turn from the other side. They are also available as a "single" cylinder which allows you to lock the door with a key from one side only. Normally the cylinders will be supplied in a brass, nickel or satin finish to match the door furniture being used.
Occasionally you will find that your handle on your door becomes loose and no resistance can be felt when it is moved. If this is your problem you may need to replace the gearbox. The gearbox is the critical component in all multi point locks and occasionally a complete system is required.
