Languages of the Indo-European family are classified as either centum languages or satem languages according to how the dorsal consonants (sounds of “K”, “G” and “Y” type) of the reconstructed Proto-Indo-European language (PIE) developed. An example of the different developments is provided by the words for “hundred” found in the early attested Indo-European languages (which is where the two branches get their names). In centum languages, they typically began with a /k/ sound (Latin centum was pronounced with initial /k/), but in satem languages, they often began with /s/ (the example satem comes from the Avestan language of Zoroastrian scripture).
https://en.wikipedia.org/wiki/Centum_and_satem_languages
