To be smart can have several meanings depending on the context. Sometimes the meaning is referring to your appearance, i.e. your clothes and general appearance is somewhere in between casual and elegant; more or less to be smart is to wear ‘formal’ clothes.
However, it can also refer to your intelligence. A smart person is a clever or intelligent person. Having said that and personally speaking, it’s very debatable whether ‘smart technology’, such as phones and cars should be called ‘smart’. In my book, surely, it depends on the hands using the devices and gadgets. Having a smart car doesn’t make you an intelligent driver.
Unfortunately, I usually never look smart and my mother is the only person who thinks I’m smart. Indeed, I have been called moronic countless times.