OK, here it is, the most easily understood view of our universe. First get a shovel and dig a hole.
Put all the dirt from the hole in one pile.
Dig until it is as big as you can make it.
Notice that the dirt you took out of the hole is roughly as tall
as the hole is deep. This is the first great cosmic truth.
This is your first grand duality. There will be dualities close to infinity like a fractal has repetitions.
Dimensions are easier to see in your head than you have ever imagined.
They are actually as simple as semi balanced directions of energies from pure positive condensed matter energy
to pure compressed space energy wit various combinations in between.
Roughly you can think of dimensions as being simply composed of energies with balanced directions
like; in-in, in-out, out in and out- out.
What keeps these dimensions separate from each other is that each dimension interacts with each other only partially
with a force they have in common or not at all.

For example if we live in the in-in dimension with 4 forces, one of which is gravity, our neighboring "dark matter" in-out dimension
may only share one force of gravity with us and
the rest of its forces do not interact with us at all.

We all have heard that our in-in matter is just compressed energy as expressed in E=mc2.
A LITTLE MASS MAKES A BIG BOOM. for example the mass of one penny has enough energy to lift a fully loaded aircraft carrier
a mile into the air, or most likely all over the place for miles.
In a similar way the out-out energy of space, a great opposite of mass, has enough energy
in a cubic centimeter to boil away one of our oceans.
But there is something holding back the incredible energy of space almost entirely as
if a great anti space energy almost equal to pure space leaves space in a condition that causes only a slow expansion
instead of space moving faster than light, as space actually does inside a black hole.

We have now just described our visible universe, dark matter and dark energy.
Now here comes a bigger mystery, as if explaining dark energy was nothing.

What has slowly changed to cause space to start accelerating? It didn't always expand faster and faster
according to measurements. It is easy to get tricked with blue sky thinking or false equivalencies so tread lightly.
What else is accelerating? Black hole formation is growing exponentially !? Did another dimension cancel out some
great forces as our dimension did when anti matter was canceled out by positive matter atoms
which was almost balanced BUT POSITIVE MATTER ATOMS OUTNUMBERED ANTI MATTER ATOMS BY ONE IN A billion. Entropy began very early in our universe AND WILL CONTINUE until there is a collapse of the fundamental energy required to hold our universe open.

THE CHALLLENGE BEFORE US IS THE DISCOVERY OF FORCES in OTHER DIMENSIONS THAT DO NOT INTERACT WITH OUR DIMENSION BUT may be CAPABLE OF VIRTUAL MAGIC IF EVER ARE THEY MASTERED. YOU KNOW, THINGS LIKE SPACE TIME.