In Lisbon you have different transport systems: Metro, Bus, Tram, Fairys, Electrico, Tuktuk, E-Scooter and Bikes. But only one card.
You must go to any station of the metropolitan, that is already the main disadvantage. Only there you can buy and get this tiny plastic card for 0,50 Euro to store your money. You cannot buy and upload it on any other vehicles.
Once you bought this card and uploaded via cash or credit card some money you are able to start your travel or comuting in Lisbon.
If you have enough credit you can step into the metropolitan station, a bus, a tram or even the historical trams, called eléctricos, validate your card in front of a ticket machine and travel to your destination. A green light or the corresponding text (“titulo é valido”) appears if everything is correct.
I normally used a daily ticket when travelling by bus and tram or a single ticket when using the metropolitan. So I was everytime fine and don’t know what happens or is to do if your credit is not sufficient. You have to take care of enough money on your card.
Conclusion / summary
For other means typical in Lisbon, Tuktuk cars, E-Scooter and bikes you have unfortunately use other solutions.
One card with enough credit works well for the urban transport system. For other options you will need still different other solutions.