Privacy coin
Monero is fungible, past transactions can not be traced, thus all coins are indistinguishable from other coins. Transaction addresses and amounts are obfuscated by design but transactions can be revealed by a user if required. Privacy of transactions mimics the use of cash in current economies.
Ring signatures
A ring signature is a way to make sure a transaction can't be tied back to a specific individual. As you transact through the network, it mixes the public information of hundreds of transactions together. (Your money is still yours. It's never commingled with anyone else's.)
Decentralisation
The smart mining forthcoming feature will allow transparent CPU mining on the user's computer, far from the de facto centralization of mining farms and pool mining, pursuing Satoshi Nakamoto's original vision of a true p2p currency.
Scalability
Monero has no hardcoded limit, which means it doesn't have a 1 MB block size limitation preventing scalability. As bitcoin has grown, the block sizes have stayed the same. This has caused the bitcoin network to slow down. It just can't handle a lot of transactions at once. For instance, the Visa payment network can handle up to 56,000 transactions per second. By comparison, bitcoin can only handle seven per second. Monero has no such preprogrammed limit. It's designed with a look-back window. That means the network reviews the preceding transactions and automatically adjusts the size of the blocks to account for transaction volume. That makes Monero scalable. And that means as more people use Monero, it will be able to grow quickly.