Ripple is a global payment protocol aimed to provide fast transactions and cheap payments internationally. The network uses a digital currency known as XRP (sometimes it's referred to as Ripple). Unlike other cryptocurrencies Ripple is not aimed to replace banks, rather this project is created to improve the work of banks (including transactions between different banks) via blockchain solutions.
Dropil (DROP) is an Ethereum token and works as a utility token for the Dropil platform. No more Dropil tokens will ever be created, which is supposed to prevent further deflation. You can buy Dropil (DROP) for cryptos (for example, BTC or ETH) with some exchange platforms.
Stellar is an open-source cryptocurrency network launched by non-profit Stellar Development Foundation. The currency itself is called Lumen (XLM). Some experts note that this asset has similarities with Ripple because of its quick and cheap transactions.
The Stellar network is guarded by the special contract that doesn't temporarily allow holders of big amounts of Lumen to sell it. Stellar works as an exchange platform where Lumen is used to pay a small exchange fee. The project has a high level of decentralization and provides equality for all of its participants. It has one of the biggest market capitalizations.