Generally they are used for power output, but the 5V one can also be used for power input if you want to power the board from 5V.

But since they are just power they have no "direction" as such, only a voltage level.

VIN is power input. IN means INput.

Generally 5V and 3.3V are used for power output, but the 5V one can also be used for power input if you want to power the board from 5V.

But since they are just power they have no "direction" as such, only a voltage level.