In todays day an age, digital effects have almost completely repalced the need for analog solutions. This is especialy true for reverb, as before digital, most reverb was either played into and recored from a physical space, or some similar electro-mechanical system, like plates and springs. In any of these cases, they can be computer modeled completely by convolving the impulse of the space with your source.
Taking an impulse can be as simple a recording a ballon pop into whatever mic you have laying around, and the ballon pop method had been prefered for some time, and suprisingly does't give terible results. However, with computational power being much less of a limit, there are much beter methods. We can use sine sweeps, to essantialy streach out the dirac delta function by frequency over a given period of time, and this is exactly what softwares like REW attempt to do. (I cant really speak to how the software works, but this is the idea in the mathmatical sense at least)