In general the models are grouped into the following categories:
SpectralModel: models to describe spectral shapes of sources
SpatialModel: models to describe spatial shapes (morphologies) of sources
TemporalModel: models to describe temporal flux evolution of sources, such as light and phase curves
SkyDiffuseCube: model to combine the spectral and spatial model components
The models follow a naming scheme which contains the category as a suffix to the class name.
The model gallery provides a visual overview of the available models in Gammapy.