In the alarm industry many people will commonly use the blanket term “siren” to describe all audible equipment attached to the control. When purchasing, as well as identifying the equipment, there is a big difference between the two.
A speaker is simply that, no circuitry between it and the alarm control. It will not generate a sound on it's own.
A siren is a speaker that incorporates the electronic circuitry, called a siren driver, necessary to generate a siren sound.
Some control panels have an integrated siren driver and offer the option of a siren output that can be connected directly to a speaker or a voltage output that must be connected to a siren.
It is important to be aware of what output or outputs a panel supports and that the output is connected to the appropriate sounding device.