The GUID is a value that the AutomaticUpdater uses to distinguish your application from all the other apps using the AutomaticUpdater. Namely, it's used when caching updates.
Do i need to change it when i do a new release?
No.
What does the guid do?
In the demo video, when using the autoupdater control it says to set a guid which i have done
Do i need to know what this is for? Do i need to change it when i do a new release?