What's the difference between protected and unsafe resources?

The resources shown at the top of the screen are in your warehouse. (The ones in your bag are always safe until you use them)

If you are attacked then the resources in your warehouse can be stolen. The warehouse has a protection level though so a certain amount is protected and cannot be stolen. This is increased as you upgrade the warehouse.

The game also now has 'Safe' resources, these are ones that you can earn through some rewards. In your bag they have a green shield icon. When you place these in your warehouse they cannot be stolen no matter how much you have. They cannot be transported to other players either.

It's a little confusing to read but in general the resources that you might lose if you are attacked will be any 'Unsafe resources' that are above the 'Protected Resources' level.