To understand what dark-energy is you must first visualize the inhabited universe we look "out" upon as literally being the "inner" content of a blackhole that exists within a (geometrically) extra-dimensional "multiverse" manifold. In other words, our "child" universe is a blackhole hyper-sphere ("time" being one of the spatial dimensions) "birthed" from the collapse of a high-density star-like object within an extra-dimensional "parent" universe.

A geometric asymptote known as an "event horizon" merely represents a lensed inversion of space-time, such that what is considered to an observer external to the black-hole to be an inward-outward spatial dimension measuring the black-hole's radii is perceived as a "time" dimension to an internal observer existing within the black-hole. The "Big Bang" is our blackhole universe's geometric singularity (when-where the hyper-star's core first started the formation of the blackhole), whereas the "Heat Death" or "Big Rip" at the end of "time" is the geometric asymptote we call the event horizon (merely approached from within).

Just as gravity is merely the curvature of space-time bending "inward," "dark energy" (anti-gravity) is space-time exhibiting an exponential exfolding (curving "outwardly"). Remove a couple spatial dimensions and imagine our universe as a funnel, with its "tip" the singularity and the "lip"/"rim" the event horizon. Now visualize numerous "world lines" (representing the space-time paths of objects) running from the tip ("Big Bang") to the exponentially widening rim (event-horizon), and, for simplicity, imagine the objects never accelerate relativistically but rather travel unaltered, "straight" paths. Those world-lines will exponentially curve away from each other geometrically as they approach the event horizon ("rim") asymptote.

Now imagine each of these world lines represents a galaxy and the progression of "time" is represented as moving spatially away from the "tip" / singularity / Big Bang of the funnel towards the "rim" / event horizon / Heat Death end. The infinite exponential stretching of space-time, as world-lines approach the event-horizon asymptote, is perceived (from the temporal perspective of the relative objects) as exponentially accelerating expansion, which ultimately takes an infinite amount of "time" to reach for an interior observer. This is exactly the same relativistic effect that is described alternatively as the quantum mechanical "smearing" of information across the event horizons of blackholes (see: holographic principle).

Now, try to extrapolate the funnel geometry to a circle, with tip as center-point and rim as circumference, while maintaining a sense of the stretching/smearing effect as a dilation of space-time.

With this simplified visualization we can see what can be approximated mathematically as a Lie Group (if allowing an infinite radius in the model to account for the logarithmic warping effect of space-time curvature). Now, recall that all black-holes have some degree of geometric spin. Imagine what happens to matter-energy falling into the blackhole due to relativistic "frame-dragging"; it falls inward following an infinite, logarithmic spiral world-line (indeed our "golden spiral" geometry is a consequence of our blackhole universe's angular momentum). Now try to grasp this geometric topology with the removed spatial dimension added back in: you have a hyper-sphere with a toroidal-vortex geometry. This internal space-time curvature is roughly analogous to the patterns exhibited by the electromagnetic fields of the Earth and Sun, and the strong-weak nuclear fields of particles, but is effectively a gravitomagnetic "de Laval nozzle" due to the toroidal-vortex geometry inducing a "Venturi effect." This geometric energy dynamo is responsible for generating the bipolar "relativistic jets" spewing from some blackholes in our universe which physicists still haven't formally understood the mechanism behind.

With this simplified visualization we can see what can be approximated mathematically as a Lie Group (if allowing an infinite radius in the model to account for the logarithmic warping effect of space-time curvature). Now, recall that all black-holes have some degree of geometric spin. Imagine what happens to matter-energy falling into the blackhole due to relativistic "frame-dragging"; it falls inward following an infinite, logarithmic spiral world-line (indeed our "golden spiral" geometry is a consequence of our blackhole universe's angular momentum). Now try to grasp this geometric topology with the removed spatial dimension added back in: you have a hyper-sphere with a toroidal-vortex geometry. This internal space-time curvature is roughly analogous to the patterns exhibited by the electromagnetic fields of the Earth and Sun, and the strong-weak nuclear fields of particles, but is effectively a gravitomagnetic "de Laval nozzle" due to the toroidal-vortex geometry inducing a "Venturi effect." This geometric energy dynamo is responsible for generating the bipolar "relativistic jets" spewing from some blackholes in our universe which physicists still haven't formally understood the mechanism behind.

Regardless, "dark energy" is not an energy at all, but our perception of the exponentially increasing global curvature of space-time as we approach the geometric asymptote that is the event horizon. Try to recognize that our perception of time is merely a perceptual manifestation of consciousness (which is the interference pattern generated by the Fourier Synthesis (quantum entanglement) of de Broglie matter-waveforms, with an effect analogous to "scanning" along these world-lines), and that world-lines are "attracted" to each other by "gravity" over "time" only in the sense that space-time is expanding/stretching less rapidly at shorter distances than at larger distances (a global form of the "Casimir effect").