Sinal de transporte
These icons are used on the objects of the transport infrastructure, such as railway stations, bus stations, airports. They indicate where you can pick your luggage, take a piss or show your passport to the customs officer (so that nobody confuses anything).
You might wonder, why? Because amateur tourists love to taste exquisite bitter cocktails before going on a trip. And that's how it starts... Trying to get your money from a coffee vending machine (instead of a bank machine), showing the customer something you were supposed to pull in the loo... and it's not a passport for sure.
In order to prevent such nonsense, we recommend you to learn these information signs in advance, using this wonderful set of emojis.