SPR is the native token to the Casper network. As a Proof of Stake blockchain, Casper relies on CSPR to reward the validators that participate in the PoS consensus mechanism to secure and uphold the network. Casper users pay the fees with CSPR. Validators and governors receive CSPR token as a reward. Casper users also rely on CSPR to pay network fees for on-chain actions. The CSPR token was available through CoinList for the initial public token sales (March 23-28th, April 7th, 2021). One can nowadays purchase tokens on certain trading platforms.
All future tokens will only be those created algorithmically to reward validators. This will be a single digit percentage inflation each year, much like in the Ethereum network.