system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is the 5th dimension?

Following the 5 dimensional black hole post i am most curious about the 5th dimension. 

To my understanding relativity covers the first 3 dimensions + time as the fourth, but does the 5th dimension cause any detectable effects on the every day human life? What exactly is the 5th dimension?
gpt
At this point, extra dimensions are purely hypothetical, and come from mathematical models of physics. Depending on the particular model, extra dimensions can be highly compacted into tiny spaces or can be very large.

As for what these dimensions "are"/ could be, this is probably beyond what we are capable of describing in any meaningful way. Similar to how a 2d creature could not possible understand 3D, we are locked into perceiving the dimensions that we perceive. As such, extra dimensions in mathematical models remain an abstraction that potentially help us explain observed phenomena.