What are the "realms" or "planes of existence"? Various suttas mention various 'planes' or 'levels' or 'realms' of existence; for example:

The Thirty-one Planes of Existence
Scattered throughout the suttas are references to as many as
thirty-one distinct &quot;planes&quot; or &quot;realms&quot; of existence into which
beings can be reborn during their long wandering through samsara.
These range from the extraordinarily grim and painful hell realms all
the way up to the most exquisitely refined and blissful heaven realms.
Existence in every realm is temporary; in Buddhist cosmology there is
no eternal heaven or hell. [etc.]
The realms of existence are customarily divided into three distinct
&quot;worlds&quot; (loka), listed here in descending order of refinement:

The Immaterial World (arupa-loka). Consists of four realms that are
accessible to those who pass away while meditating in the formless
jhanas.

The Fine-Material World (rupa-loka). Consists of sixteen
realms [etc.]

The Sensuous World (kama-loka). Consists of eleven realms [etc.]


The information on this page was assembled from a variety of sources.
In the interests of economizing space I have not attributed each fact
to its respective source.

I don't want to ask for a precise list, but how or what should I  understanding these realms are?
I have heard several versions now of what &quot;levels of existence&quot; are:

Some say it is like physical, or is it mental (psychological), biomes in this universe?
Others say it is other universes or even other dimensions?
My understanding of "levels of existence" is that they are mind states.For example when i'm happy i am residing in the deva realms and when i'm sad or angry in the lower realms.These mind states keep changing and fluctuating all the time it never lasts.As for real physical places I think the only way to find out for certain is through meditation.