The basic ideas and results of the theory of self-trapped electron and hole states are reviewed. The basic features of self-trapping as an important and quite general phenomenon as well as the basic types of self-trapped states (polarons, fluctuons, and electron pairs with a negative correlation energy) are studied. The characteristic features of self-trapping on defects in a crystal lattice, in disordered systems, and in amorphous structures are compared with self-trapping in regular crystals. Some pressing problems in the modern theory of self-trapped electron and hole states in solids are noted or briefly discussed.

@article{Klinger:1985,
	author = {M. I. Klinger},
	title = {Self-trapped electron and hole states},
	publisher = {Physics-Uspekhi},
	year = {1985},
	journal = {Phys. Usp.},
	volume = {28},
	number = {5},
	pages = {391-413},
	url = {https://ufn.ru/en/articles/1985/5/e/},
	doi = {10.1070/PU1985v028n05ABEH003797}
}