A model that scores how believable a sample is with an energy function.
An energy-based model gives every sample a weirdness score. Normal ones score low, strange ones score high. Walk the score downhill and it can even build or fix a sample.
People use it to make examples, fix messy ones, or spot odd data. Training is slow because sampling is hard.
Generative Model
An Energy-Based Model can generate samples by looking for low-energy areas.
Boltzmann Machine
A Boltzmann Machine is a classic early Energy-Based Model.
MCMC
Energy-Based Models often use MCMC to sample from low-energy areas.
PGM
Many Energy-Based Models can be seen as undirected PGMs.