The Light Echo is an Inner Plane which sits parallel to The Prime Material Plane, sometimes known as The Feywild or The Plane of Faerie. It is mostly inhabited by fey creatures.
The Light Echo reflects places on The Material Plane, but it is a realm of everlasting twilight. It is a plane of nature and magic, and the reflections are not always literal. Where a great tower exists on the Material Plane, an ancient oak might exist in its place in The Light Echo.
Travel
Travel to the Light Echo can happen by accident, as crossings manifest in places of great natural power on The Material Plane. A crossing might be a clearing in a forest, a circle of mushrooms, or a hole under the trunk of a tree. Often these crossings open infrequently, for example only during a full moon or during a solstice, or only if the traveller is carrying a particular item.
Travel to this plane can also be achieved through various spells, or via The Ethereal Plane.