A software daemon is some bit of software that runs independently of human control. We have been creating them for most of computing history. But the majority are not that important. Nobody knows their names. Nobody really cares that much if they have bugs. If one stops working you restart it and move on with your life.
Cryptocurrency blockchains are also daemons. Each blockchain is just software that performs whatever tasks it is programmed to do. The interesting differences are the scale and the distributed nature of the blockchain. Millions of people contribute hardware to run blockchain software as opposed to a cronjob running only on my laptop.
The Ethereum blockchain is a billion dollar distributed computing platform powering things like DNS names (ENS) and art NFTs. Anyone can submit a ‘contract’ to Ethereum as it is essentially a daemon that runs other daemons. Compared to the log daemon that collects logs on your computer, Ethereum is immensely larger. Restarting your log daemon is essentially a free operation. Restarting Ethereum from zero would cause billions of dollars of losses.
Due to their decentralized nature it is also impossible to ‘stop’ a blockchain software daemon. Ethereum exists on millions of computers and as long as even one of those copies continues to operate Ethereum will continue to exist.
People also care enough about these blockchains that they have names. You have the ‘Ethereum Classic’ and ‘Eth2’ daemons which run very similar software, yet their identity is actually important to humans. Millions of copies of Linux and Windows are running right now, but none of them are important enough to have names.