A ConcurrentHashMap is a thread-safe collection in Java that allows multiple threads to read and write data simultaneously without causing data inconsistency. It achieves this by dividing the map into segments, enabling concurrent access to different segments, which improves performance compared to traditional synchronized maps. This data structure is part of the java.util.concurrent package and is designed for high concurrency. It provides methods for adding, removing, and retrieving key-value pairs, ensuring that operations are atomic. This makes ConcurrentHashMap ideal for applications where multiple threads need to access shared data efficiently.