Serum is a decentralized exchange (DEX) founded by the team that earlier, in 2019, was engaged with the FTX Foundation development. Being among the earliest projects on Solana, Serum initiated the idea of a fully decentralized high-speed exchange with lowest network fees among other crypto exchanges. Unlike the majority of exchanges that work as an AMM, Serum brings book trading, typical of centralized exchanges, into DeFi. 
Apart from offering exchange functionality, Serum is building a whole ecosystem with a number of applications based on it, from gaming platforms and oracles to AMMs. 
The Serum coin (SRM) is integrated into the platform for charging fees and powering the burning process. SRM holders benefit from a 50% discount for all transactions. The project has also introduced a governance system based on SRM, yet, only a few parameters of the ecosystem can be modified following a vote.