It would be easier or you to explain is in words of 3 syllables or less... And Wikipedia can be so unreliable at times.
As I remember it, a capacitor has two plates and a non/semi conductive material (a dielectric) between them. Electricity builds up on one plate until it surpasses the threshold of the dielectric material of holding back the charge and then the charge is set through to the other plate until the charge reaches zero and the dielectric material is able to block again. This, as I say it sounds like, switching on and off at a fast rate.
A transistor is a switch to allow current to go through two pins depending if the third pin of the transistor is activated by a charge or not. Thus the difference is as I see it, a Transistor is either on or of, and a capacitor is pulsing on, off, on, off at a steady frequency depending on the dielectric material and surface area of the plates.
Help us here and correct me if I'm wrong. We all need to learn.