Speakers also known as earpiece is the device that allows the handset user to hear the other user during call convesations.
While the Buzzer or a Ringer is the one that sends out the ringtone to be heared by the handset user.
Both Earpiece, buzzer or ringer are same speaker. it only varies the loudness of it sounds being produce.
Ringer buzzer generates more loudness than the earpiece speaker.
A speaker is a device that converts electrical signal into sounds.
It is made by a magnetic wire winded into a coil and a metal piece of magnet.
below is an example oh how to test of a good and working speakers .
Simply set the analog or digital multi-tester to X1 resistance value, and attach one probe to one the speakers terminal while tick tacking the other one unto it.
A working speaker produce a crackling sounds and the multi-tester pointer moves, while the a busted one will not and have no reading.