Aether is a magical energy that’s found throughout the Multiverse, but it’s become an integral part of the ecosystem on Kaladesh. Refined aether is the primary power source for most of Kaladesh. On cards, this magic energy is represented by energy counters, a new kind of counter that players can get.
Most cards that give you energy counters also give you a way to spend them. Note that it’s you, the player, who gets the counters. For example, if a creature has an ability that gives you some energy counters when it enters the battlefield, you keep those energy counters even if that creature later leaves the battlefield. Energy counters don’t go away as phases or steps end. Energy counters don’t go away as the turn ends. The only way for you to lose them is to spend them. Energy counters that you get from one card can be saved up and spent on abilities of other cards. So having eight lands enter the battlefield is one way for the Architect to summon a Beast for you, but there are faster ways.
Please see Wizards of the Coast for the complete guide on all things Kaladesh, and from where we got this information.