supercomputers are basically a completely different kind of computer to a desktop, or a server, or even a more conventional cluster of servers in a datacenter.

supercomputers are basically a completely different kind of computer to a desktop, or a server, or even a more conventional cluster of servers in a datacenter. What makes the biggest difference is the interconnectivity: supercomputers use very high bandwidth and low latency links like infiniband between the nodes. What this enables is distributed processing of tasks which are a lot less easily parallelised than the kind of thing you can do with a distributed system. For the most part this is things like simulations, where every part can depend on every other part from one iteration to the next, and you can basically always increase the resolution of these simulations to fill the compute available and get better results. Yes, with general computer advancements a regular workstation can now equal an older supercomputer, but it has to be few decades old supercomputer.