Hello @jia liang
Both MSRA and Quick Assist are used for users who need help from IT professionals in enterprise internal networks
MSRA is more older, while Quick Assist is a newer tool that was introduced with Windows 10.
MSRA is more suitable for IT professionals who need to provide remote assistance to users. Quick Assist is more suitable for users who need help from IT professionals.
MSRA is more powerful than Quick Assist but requires more setup and configuration.
Where Microsoft Remote Desktop is a remote desktop tool that allows you to connect to a remote computer and control it as if you were sitting in front of it. It is more suitable for IT professionals who need to remotely manage computers and servers.
More information:
Use Quick Assist to help users
How to Use Microsoft Remote Assistance (fastie.com)
Best regards
Karlie