Cassandra is a powerful, open source NoSQL database designed to provide a highly available, distributed data store. It's built on a peer-to-peer architecture and offers excellent scalability and high availability, making it an ideal choice for large scale applications. It uses a column-oriented data model and a query language called CQL, which makes it easy to query large datasets. Cassandra is also highly resilient to failure, with its masterless, distributed architecture which allows for data to be replicated across multiple nodes. It's an excellent choice for applications that require low latency and high throughput. Developers appreciate Cassandra's ease of use and its ability to handle large datasets with ease.