Unlike selectively transparent alternatives (e.g. Zcash), Monero is the only major cryptocurrency where every user is anonymous by default. The sender, receiver, and amount of every single transaction are hidden through the use of three important technologies: @Stealth-Addresses, @Ring-Signatures, and @RingCT.
Because every transaction is private, Monero cannot be traced. This makes it a true, @fungible currency. Merchants and individuals accepting Monero do not need to worry about blacklisted or tainted coins.
With Monero, there are no wire transfer or check clearing fees, no multi-day holding periods, and no fraudulent chargebacks. Because Monero is decentralized, it is not constrained by any particular legal jurisdiction and provides safety from capital control.
Monero was launched in April 2014. It was a fair, pre-announced launch of the CryptoNote reference code. There was no premine or instamine, and no portion of the block reward goes to development. See the original Bitcointalk thread