A Hive mind or Cluster is a group of people or bodies, who can be addressed as one person. Hive minds share computing power or brain capacity and often will have access to a central pool of memories and thoughts.
When the brain-to-computer interface was invented, it became possible to share thoughts and memories directly without any intermediary, as well as telepathic communication. Later, with the advent of digital-born beings, it became possible for two people to effectively merge into a singly addressable person, sharing thoughts and memories.
In humans, it has always been possible for two or more people to occupy a single body. Technology to upload consciousness made it possible in some cases to choose the amount of headmates and let headmates join and leave bodies at will. Not all hive minds consider themselves plural and not all plural people consider themselves hive minds. There are many types of hive minds, including more loosely coupled networks of people that retain a large amount of mental and physical individuality, or one person occupying multiple bodies. It differs in this sense from plurality, which is defined as multiple people occupying the same body, whereas hive minds don't have to be contained in one body or even be corporeal at all.
While digital and synth born people always have the option to inhabit multiple bodies, some humans also choose to have their consciousness extracted and inhabit more than one body to be able to multitask or even experience multiple lives simultaneously. In the first case, the multiple bodies of the same mind usually live in one place. In the second, all bodies might be in completely different places, own different houses and have a completely different social circle.
Digital beings are considered hive minds if they run on multiple servers at once while retaining shared consciousness or if they are connected to one or more physical bodies. Some digital born people choose to confine themselves later to a singular physical body or a singular digital residency, but most of them embrace multiplicity.