Very fine resolution, highly sensitive to light. Radio wavelengths are very large - on the order of several cms long. In order to gather the information from light, the light must be gathered from an area much larger than the wavelength in order to have any reasonable resolution. Interferometry is the process of electronically linking two or more telescopes as they are observing the same object at the same time. This process allows the two or more telescopes to act like one large telescope and get much better resolution than any telescope acting singly.
Different objects emit light at different wavelengths.
Some objects that look normal in one wavelength can look much different at other wavelengths. Some objects emit light only in certain wavelengths. For example, if an object only emits radio waves, then if you will never find it if you only look in the visible wavelength range.