In the traditional financial industry, Certificates of Deposit (CDs) are offered by retail banks and they typically offer a slightly higher interest rate than would be available in a standard savings or checking account. To achieve this higher rate, depositors must agree not to withdraw their funds - usually for one, three, or six months, and sometimes up to five years. The funds are government guaranteed and CDs are an easy way to earn a little extra interest - risk free - on unused funds that would otherwise be held in a current account.
The HEX project says it is attempting to create a decentralized blockchain-backed version of traditional CDs. Apparently HEX is designed to pay interest to participants who lock up their coins through stake. Those who stake their HEX for longer periods get higher rewards, paid out in HEX tokens. According to HEX, interest payments range from 3.69% to 369% depending on how much of the total HEX token supply is being staked. HEX includes large referral bonuses for participants who bring in newer participants. These participants are entitled to more bonuses as they introduce new people to the project.