What exactly does the excitation spectrum tell us about a sample in Florescence Spectroscopy, what information does it tell us? I know that we will get an output of concentration vs intensity but that's it.
I know that we will get an output of concentration vs intensity but that's it.
Actually, that's not what you are getting. Typically, you run an emission spectrum first to determine the maximum of the fluorescence emission (or any other point of interest in the emission spectrum). In the excitation spectrum, you monitor this particular emission line and its intensity while varying the excitation wavelength.
According to Wikipedia,
by analysing[sic] the different frequencies of light emitted in fluorescent spectroscopy, along with their relative intensities, the structure of the different vibrational levels can be determined.