Short answers, pulled from the story.
Evangelista Torricelli produced the first laboratory vacuum in 1643. He filled a tall glass container closed at one end with mercury, then inverted it in a bowl; the mercury column dropped and left a near-empty space at the sealed top, now called a Torricellian vacuum.
A human exposed to vacuum loses consciousness within seconds and would die of hypoxia within minutes. Blood does not boil because blood vessel pressure keeps the boiling point above body temperature of 37 degrees Celsius, but gas bubbles can form in bodily fluids, a condition called ebullism, and the body may swell to roughly twice its normal size.
In 1654, Otto von Guericke invented the first vacuum pump and used it to partially evacuate two hollow metal hemispheres. Teams of horses harnessed to each side could not pull the halves apart, demonstrating the force of atmospheric pressure pressing inward on the evacuated sphere.
According to ISO 3529-1:2019, high vacuum falls below 0.1 Pa, while ultra-high vacuum falls below 1 micropascal. Ultra-high vacuum requires low-carbon stainless steel, metal seals, special surface preparation, bake-out procedures, and high vacuum pumps, whereas high vacuum can be achieved with elastomer seals and standard stainless steel.
QED vacuum is the lowest-energy state in quantum electrodynamics, containing no matter particles and no photons. It is not truly empty because the electric and magnetic fields within it have non-zero variances, producing vacuum fluctuations in which virtual particles briefly hop in and out of existence; experimentally verified effects include spontaneous emission and the Lamb shift.
Lucretius argued in the first century BC that a void must exist to allow motion. Aristotle rejected the vacuum in his Physics, arguing that motion through a medium with no impediment could continue forever with no reason to stop, making physics incoherent. Hero of Alexandria attempted and failed to create an artificial vacuum in the first century AD.