Because it is made up of 4 dimensions, 3 spatial and one temporal.
A location in space is specified by three coordinates, for example x, y, z or latitude, longitude, altitude. A "location" in time is specified by one value. Together, these can be used to specify a location in space-time (known as an "event"). So we end up with four-dimensional space-time.
Temporal means related to time. Space <-> spatial; time <-> temporal.
(It is, of course, also related to temporary - for a short time. It's from Latin, you know.)
It looks like the first part of this is just based on a misunderstanding of "temporal".
There is more to existence than energy. (Mass, electric charge, colour "charge" of quarks, etc)