Network emissions are XRD tokens that are created automatically by the Radix Protocol to incentivize XRD token holders to help secure the Radix Public Network by staking in Radix’s Delegated Proof of Stake (DPoS) system. They are also to incentivize node-runners to operate reliable, performant validator nodes.
XRD emissions are emitted at a rate of approximately 300m XRD per year. The majority of these emissions will be provided to XRD token holders who delegate stake to validators. Validator node-runners are also entitled to set a validator fee which will be a % of the emissions provided to the XRD that is staked to their validator node.
A further 600m XRD is held in reserve by the Radix Foundation and may be used to subsidize node-runners at its discretion. This is a manual subsidy and is separate from network emissions. You can read more about this here: What is the XRD subsidy incentive for validators?