  Photon emission correlation spectroscopy is an indispensable tool for the
study of atoms, molecules, and, more recently, solid-state quantum defects. In
solid-state systems, its most common use is as an indicator of single-photon
emission, a key property for quantum technology. Beyond an emitter's
single-photon purity, however, photon correlation measurements can provide a
wealth of information that can reveal details about its electronic structure
and optical dynamics that are hidden by other spectroscopy techniques. This
tutorial presents a standardized framework for using photon emission
correlation spectroscopy to study quantum emitters, including discussion of
theoretical background, considerations for data acquisition and statistical
analysis, and interpretation. We highlight important nuances and best practices
regarding the commonly-used $g^{(2)}(\tau=0)<0.5$ test for single-photon
emission. Finally, we illustrate how this experimental technique can be paired
with optical dynamics simulations to formulate an electronic model for unknown
quantum emitters, enabling the design of quantum control protocols and
assessment of their suitability for quantum information science applications.
