The Satem division of the Indo-European family includes the following branches: Indo-Iranian, Baltic and Slavic, Armenian, Albanian, perhaps also a number of barely documented extinct languages, such as Phrygian and Thracian (see: Indo-European languages). All those languages show the characteristic change of the so-called Proto-Indo-European palato-velars (*k^{^}, *g^{^}, *g^{^h}) into affricate and fricative consonants articulated in the front of the mouth. For example, *k^{^} became Sanskrit s′, Avestan, Russian and Armenian s, Lithuanian s^{^}, Albanian th, etc. At the same time, the protolanguage velars (*k, *g, *g^h) and labio-velars (*k^w, *g^w, *g^wh) merged in the Satem group, the latter losing their accompanying lip-rounding.

By contrast, in the remainder of the Indo-European family (the then-called Centum languages), palato-velars lost their palatal component and merged with plain velars, while labio-velars remained distinct.

The Satem shift is conveniently illustrated with the word for '100', Proto-Indo-European *k^{^}mtom, which became e.g. Avestan satem (hence the name of the group), Lithuanian s^{^}imtas, Russian sto, etc., as contrasted with Latin centum (pron. [kentum]), English hund(red)- (with /h/ from earlier *k, see Grimm's law), Greek (he)katon, Welsh cant, etc.

The Satem group is a paraphyletic group and thus not a phylogenetic unit.