"What is this thing?"
This disambiguation page lists articles associated with the same title. If a link led you here, you may wish to change that link to point directly to the intended article.
Echo refers to several subjects in the Metroid series. You may be looking for:
Echo Visor
Echo Gate
Echo Hall
Echo Key Beam system
Echo Fighter, the official term for a Super Smash Bros. character whose moveset is based on another character