Oracle Coherence is an in-memory data grid solution that enables real-time data storage and access across distributed systems. It provides fast and reliable access to data by storing it in-memory, allowing applications to access this data quickly without going to disk. Oracle Coherence is used in various applications such as financial services, e-commerce, telecommunications, and healthcare, among others. The skillset required for Oracle Coherence includes experience with Java, distributed systems, and data storage and retrieval mechanisms.