1. Multiple processes accessing a resource at the same time
Solution: access to common resources or a piece of code through serialization of multiple threads, fast, suitable for controlling data access.
2. Multiple instances of a single resource
Solution: designed to control a limited number of user resources. It allows multiple threads to access the same resource at the same time, but limits the maximum number of threads that can access the resource at the same time. A mutex is a special case of a semaphore, when the maximum number of resources in the semaphore is equal to 1.