black box next to fuel filter

[rocket0000]

hi guys,,,, i was just working underneeth checking fuel lines than i saw a black box next to the fuel filter i was just checking it and suddenly i noticed a rubber hose just fell down and maybe it seems that it was attached to this box so i reattached it to that box and i followed it till the end to see where its coming from and it ends up under the fuel cap from inside the car.
my question does this rubber hose or tube belongs correctly to the black box?
why there is a rubber hose coming from the fuel cap ending up to this black box??

thanks

 

[Mick1988]

The black box is the fuel vapor canister and the hose is the ventilation hose.

 

[rocket0000]

thanks mate but does that hose must be attached to that box???
and what does the fuel vapor canister do?

 

[accentstencil]

The hose should be attached to the canister.
Fuel vapor canister

 

[rocket0000]

thanks mate.