Need more information on CONTEXT System variable

Hi,

I am trying to understand how the system variable 'CONTEXT' works during web-edit mode and publish.

When we apply template through 'Change Layout' option in web-edit mode, I understand that the template chosen is getting saved only in the context variable and not in the asset.

While the page is rendered, the template is read from the context variable and the asset is rendered. This is fine. My question is, how this change is getting transferred to the destination server while publishing the assets, if it is not part of the asset.