Project restore points serve the purpose of opening an ETS project in one of its earlier stages.
If a project contains invalid data, after e.g. a power failure (laptop battery), then the project is still in the project overview, but it will be grayed out, which means that it can no longer be opened for editing, the solution in such a case is to use one of the restore points in order to make the project available again for editing.
To use a restore point, click the 'Quick actions' menu from a project tile on the dashboard, then 'Restore' and select any restore point that is needed.
A restore point can either be an explicit entry, which is indicated with a 'clock' icon, or a project backup into the archive, which is indicated with a 'file' icon.
When a restore point is called up from the context menu, the associated (current) project is overwritten by the (older) project from the restore point.