They're for accessing the flash memory I think - but actually none of the ESP8266 pins will be usable anyway, because the ESP8266 will be running the AT command firmware - it's the STM32 that all the pins will be connected to.
Well, the pins will be usable if you flash Espruino onto it and tack on flying leads...
I don't see how the pins would be particularly interesting in that case though, since you've got plenty of pins on the Espruino itself, all of which are a lot more capable.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
They're for accessing the flash memory I think - but actually none of the ESP8266 pins will be usable anyway, because the ESP8266 will be running the AT command firmware - it's the STM32 that all the pins will be connected to.