A binary semaphore is a synchronization tool used in computer science to manage access to shared resources. It can take only two values: 0 and 1. When the value is 1, it indicates that the resource is available, while a value of 0 means the resource is currently in use. This mechanism helps prevent conflicts when multiple processes or threads attempt to access the same resource simultaneously. Binary semaphores are often used in operating systems and concurrent programming to ensure that critical sections of code are executed safely. They are simpler than counting semaphores, which can hold multiple values, making them ideal for situations where only two states are needed. This simplicity helps improve efficiency and reduce the risk of errors in resource management.