Vacuum is an area without air. Vacuum is common for space. Vacuum isn't empty, but it only has a small quantity of matter. Intergalatic void has less matter than Interstellar void, but the reason is unknown. Only a few living organisms living in harsh situtations can survive the void like tardigrades. These animals are microscopic organisms that live almost everywhere in fresh water. It survives it by wrapping their DNA into clouds of protein. Vaccum also has some effect like the so called 0 gravity or weightless. This has to be with the happiest thought of Einstein (yes, this was actually the happiest thought of Einstein). A man falling from the roof. That man, when he got to his terminal velocity, he would experience weightless. That happens in the vaccum when you are in the ISS like. In the Moon or other planets no, because they have a gravity field. In the ISS you experience weightless which has some side effects liike the bones start to soften because they don't need to make strength. Their sight is usually turve when they get back to Earth. This does not happen when falling from a roof because you only experience weightlessness for mere seconds or even less than that. Vaccum is also little explored and very few people have ever experienced it (every people that got to space, around 500 people with only 3 deaths). Vaccum has also little pressure so any matter that exists there won't interfere in any processes occurring there.