Energy is absolute, but on the other hand it's very abstract. Energy is not a thing, not a substance, not measurable, but on the other hand it's impossible to talk about anything which has happened without talking about the energy involved.
Energy is calculable. It should be possible to calculate all the energy which was in the singularity which caused the Universe, and that would be the same number as the total energy of the universe today. Energy cannot be created or destroyed, just moved from place to place or form to form. (I'm sure you'll have heard that!)
And maybe that's as far as we need to understand about energy. It's just a number that we can calculate that is the same before as it is after. It's just a law of conservation. But it may just be the fundamental law. You can't get something for nothing. The total energy before is the same as the total energy afterwards. All things tend towards entropy. Thermodynamics 1.
Energy | GCSE