There have been a number of Windows Registry books that provide an overview of the registry. The best content comes from searching the internet and Microsoft Learn.
There doesn't appear to be much available on LaunchProtected because it centers around security and protecting processes. There are some search results to determine what it does:
Result 1 - The Evolution of Protected Processes Part 2: Exploit/Jailbreak Mitigations, Unkillable Processes and Protected Services
Result 2 - Taking ownership over processes
Result 3 - 0patching the "Worst Windows Remote Code Execution Bug in Recent Memory" CVE-2017-0290
Why are you asking about this specific value?