You've probably been hearing about this coin as they have just been listed on several exchanges such as Kucoin, Coinall, QBTC, and BigOne. The mainnet launch was successfully executed on January 15th.

Now I already know what you're thinking, isn't there already a fundamentally decent privacy coin out there called Monero? Why yes, there is indeed. So, obviously I'm not here to tell you to FOMO in to a "super-amazing ground-breaking" coin. The concept seems good, but it will simply remain to be seen as to how it performs over the long term compared to its pre-existing competitor in the privacy crypto lane. It still has several bigger exchanges to get listed on before it gets much further.

First announced in 2016, Grin Coin is minimalist implementation that utilizes the MimbleWimble protocol. Designed for privacy and scalability, on this blockchain there aren't any addresses or amounts and storage will require only a fraction of the average capacity used by other cryptos. The development of the Grin and MimbleWimble project is 100% open source and they are also proud to let everyone know they are not cool with ICOs, pre-mining, or allowing founders' rewards.

Source: Grin-Tech Official Website

Per the official GitHub page, the following items act as the guidelines for development of this project:

Clean and minimal implementation, aiming to stay as such.
Follows the MimbleWimble protocol, which provides great anonymity and scaling characteristics.
Cuckoo Cycle proof of work.
Relatively fast block time (a minute).
Fixed block reward over time with a decreasing dilution.
Transaction fees are based on the number of Outputs created/destroyed and total transaction size.
Smooth curve for difficulty adjustments.

They also offer a more in-depth introduction on Grin and MimbleWimble here that covers technical functions and the algorithms used by the protocol.