What’s the nature of the entity summoned by mage hand?

What does a mage hand look like?

⁢According to Player’s Handbook, mage hand is a conjuration cantrip available to bard, sorcerer, warlock and wizard, that summons "a spectral, floating hand".

But what exactly am I conjuring? Is it a ghost, a construct made out of raw force, my astral/ethereal/etc body part? Do I choose the side of the hand (left or right)? Could you summon other body parts or something more abstract (like a force tentacle from the ground)?

I have many questions about the lore side of this spell in D&D, so my question is focused on sourcebooks. Thank you