Monero is a cryptocurrency focused on privacy. Transactions on the Monero blockchain are untraceable, meaning that they cannot be linked back to a specific user. This makes Monero a popular choice for users who value their privacy and security. 
Monero is also notable for its use of ring signatures, which make it more difficult for outside observers to determine which outputs belong to which inputs. This makes it more difficult to track Monero users, even if some of their transactions are public knowledge. Monero is also unique in that it uses a proof-of-work algorithm that is conducive to CPU mining, as opposed to GPU or ASIC mining. This makes it more accessible for individual miners, as they do not need to invest in expensive hardware.
Overall, Monero is one of the most private cryptocurrencies available today. However, this increased privacy comes at the cost of reduced fungibility, as some exchanges may be unwilling to accept coins that have been involved in illicit activity.