What does this mean?
Prior art also known as state of the art means something is not protected by any property right (anymore). It is free to be used by anyone for every purpose without any restrictions or conditions.
A good example is a string used to tie a regular knot. However. It might for example happen that you have a string from a new material. This material might be protected and not prior art. Therefor your string is also not protected.
for example from wool: prior art
from wool but also with a wire inside to conduct electrical signals in wearables: might be protected
a regular M4 bolt is prior art.
A regular M4 bolt though from a material that explodes for example or has an RFID chip build in might be protected
So also with prior art. Look twice. Who made this piece. And is something added that might be protectable and be protected. Go for the simplest, easiest oldest solution. And you’ll be sure.