Arduino for STM32

Hi,

Formally, the difference is clear enough. Well, off the record: are those 3.3V pins equally intolerant of any use with 5V in the circuit? I suspect, for instance, that the usual LED + resistor arrangement won't kill the 3.3V pin even if the pull-up is connected th 5V. Is it really so?

Accordingly, tolerant pins have diodes that sink currents, but they still require a high enough resistor to limit the currents going into the pin.
For non-tolerant pins you are taking your chances
http://www.emcu.eu/000/STM32_5VtolerantIO.pdf