I recently heard of a new cryptocurrency (or maybe it's not new and I'm just out of the loop) called Gridcoin which uses your GPU/CPU/ASIC to do research calculations rather than "meaningless" calculations.
I had previously thought that Bitcoin miners have your computer do calculations required to process Bitcoin transfers, and then takes a little bit off the top as payment for doing the calculation. If that's true, then why do all the Gridcoin articles say that the calculations are useless?
I'm trying to understand the actual details behind Bitcoin further, and there's very little information out there that's accessible to the layman.
What does the miner have my computer do when I'm mining? And why weren't "more useful" cryptocurrencies such as Gridcoin developed earlier? Why does the system reward you for meaningless calculations, and how is that sustainable?