What is the meaning of Equal_temperament?

A tuning system in which every interval, as a ratio of frequencies) is some exactly positive integral power of some smallest, other than the unison, base interval. In particular:

  1. Twelve-tone equal temperament: The European semi-harmonic interval compromise among the chromatic notes.

Twelve-tone equal temperament: The European semi-harmonic interval compromise among the chromatic notes.

Source: wiktionary.org