The diode included with your Ring Video Doorbell is an important item used to connect your Video Doorbell to an already existing doorbell's digital bell. It should not be used with a mechanical bell or if you're not connecting the Ring Doorbell to a bell. The video below gives more detail on when you should and shouldn't use the diode.
To find out if your door chime is mechanical or digital, the simplest method is to listen to the sound your bell makes when you ring it. If it makes the traditional "Ding Dong" sound, it is most likely a mechanical bell and the diode should not be used. You can also take the cover off of your bell and take a look inside. If you see a mechanical striker as pictured below, then you have a mechanical bell.
If, on the other hand, your bell consists of a speaker that plays a melody, it's a digital bell and you must use the diode (pictured below) included in the box.
I have a digital bell, connecting your Ring Video Doorbell to an electronic bell is a fairly simple process. Click here for step-by-step instructions.