There are two basic kinds of things that you can work with in pysynphot: a Spectrum and a Bandpass.
A Spectrum can be created from a file, from arrays, or using one of the available analytic forms.
A Bandpass can be created from a file, or from an obsmode string.
Spectra can be added, or multiplied by a constant or a Bandpass; Bandpasses can be multiplied together.
Spectra can be redshifted, renormalized, written to files, and converted from one set of units to another.
Once you have created and manipulated your Spectra and Bandpasses as desired, you can simulate an Observation, which is a special-purpose Spectrum. You can calculate the countrate and effective wavelength of an Observation.