Bitcoin is a peer-to-peer digital currency. Peer-to-peer (P2P) means that there is no central authority to issue new money or keep track of transactions. Instead, these tasks are managed collectively by the nodes of the network.
Monero is a digital currency that is secure, private, and untraceable. It is open-source and freely available to all. With Monero, you are your own bank. Only you control and are responsible for your funds, and your accounts and transactions are kept private from prying eyes.
DASH is an open source peer-to-peer cryptocurrency that uses a system called Darksend to add privacy to transactions. It allows you keep your finances private as you make transactions, similar to cash.