This logo indicates compliance with the WEEE (Waste Electrical and Electronic Equipment) Directive. The WEEE Directive is upheld by 27 countries in the European Union and represents their desire that devices like the iPhone be disposed of in an environmentally friendly way, rather than thrown in the trash as electronic waste.
But we just call it the “Nonchuckable” logo. It means: don’t put this thing in the trash, it’s got bad stuff in it that could leach into the landfill or into groundwater!