Final answer:
The two broad categories of thread implementation are user-level threads and kernel-level threads, with user-level threads managed in user space and kernel-level threads managed by the OS kernel.
Step-by-step explanation:
Thread implementation can be broadly categorized into two types: user-level threads and kernel-level threads.
User-level threads are managed without kernel support, whereas kernel-level threads are directly supported and managed by the operating system kernel. User-level thread operations, such as creation, scheduling, and synchronization, take place entirely in user space. This can make them more efficient in terms of creation time and context switch time since they don't require system calls. However, if one user-level thread performs a blocking operation, then the entire process may block.
On the other hand, kernel-level threads have full operating system support which allows for better multithreading in multiprocessor environments and better handling of blocking system calls since each thread is individually managed by the kernel.