Screen Sharing is the default system tool that can be used in macOS to allow the technician to view the screen simultaneously with the user. Screen Sharing is a built-in app that lets users share their Mac screen with another Mac on the network. The user can enable screen sharing in the System Preferences > Sharing pane, and then allow other users to request or enter a password to access their screen1. The technician can launch the Screen Sharing app from the Spotlight search or the Finder sidebar, and then enter the user's name, address, or Apple ID to connect to their screen2. Remote Assistance is a Windows feature that allows users to invite someone to help them with a problem on their PC3. Remote Desktop Protocol (RDP) is a protocol that allows users to connect to a remote computer over a network4. Virtual Network Computing (VNC) is a technology that allows users to share their screen with other devices using a VNC viewer app1. These are not default system tools in macOS, although they can be used with third-party software or settings.
References: 1: https://support.apple.com/guide/mac-help/share-the-screen-of-another-mac-mh14066/mac 2:
https://www.howtogeek.com/449239/how-to-share-your-macs-screen-with-another-mac/ 3:
https://support.microsoft.com/en-us/windows/solve-pc-problems-over-a-remote-connection-b077e31a-16f4-2529
4:
https://docs.microsoft.com/en-us/windows-server/remote/remote-desktop-services/clients/remote-desktop-protoc