NEM stands for New Economy Movement. According to the team, NEM aims to "service enterprise blockchain markets and extreme versatility in servicing diverse markets".
XEM is the native currency of the NEM public blockchain, which was launched in 2018.
It is used to pay for transactions on the NEM public blockchain. It is used to incentivize the network of public nodes to process and record transactions for participants.
According to the team, its core characteristics are zero-inflation (the amount of XEM tokens in the ecosystem is fixed), scalability (owing to a high TPS ~ 4,000 TPS), ecosystem support (through the harvesting of XEM tokens), and power-efficiency (with negligible electricity and hardware costs relative to PoW blockchain).