Resonator refers to the part of an instrument that amplifies the tone and gives it its own unique characteristics. Resonators make a French horn sound like other French horns and unlike a trumpet, because all French horns are pretty much the same shape, while the trumpet is a little different. The shape of each individual singer’s resonators cause my voice to differ from yours, and your voice to sound different when you change the shape inside your mouth.The sound created by the vocal cords is very small and unimpressive. The pharynx (the area above the larynx, where you usually feel a sore throat) and mouth are used to amplify it and make it beautiful. (There may be other resonators, too, but larynx to lips includes most of the resonating space.) The vibration of the air in that space is initiated by the buzzing of vocal folds. By altering the shape of the mouth and throat, you alter the resulting sound, or timbre. (Pronounced tam-ber.)
You also enunciate using these same changes of tongue, palate, jaw, etc., which means that diction is a function of resonance. You are limited in how much you can change the shape inside your mouth and throat, which is why you will always sound like you, but hopefully always improving, and finding more and more beautiful ways to use your own unique voice.