Radio telescopes can be used to understand continuum emission from radio sources or can be used to study the presence of atoms and molecules, which are called as mapping and spectroscopy, respectively. They can also be used to study polarized emission and/or time variability of any of the above phenomenon. We also can get the spectrum of the source at different frequencies, which can be used for understanding of the physical conditions of the emitter.
To describe an astronomical object completely, the direction of radiation, knowledge of its spectrum, details of full set of Stokes parameters, and the variation of the intensity as a function of time is needed.