Those pins are power, ground, and the two I2C pins. When connecting an original Raspberry Pi A or B, those I2C pins need to be wired to the Pi’s single I2C bus. Starting with the Pi A+ and B+ ...

the Raspberry Pi 4 has six SPI controllers, six I2C controllers, and six UARTs – all on its 40-pin header. You can’t make use of all of these at once, but with up to four different connections ...

Today is Pi Day. 3rd month, 14th day. It's not the 314th day of the year; that’s November 10th.