Category "fsck"

My Ubuntu does not boot, and the the error during that is "UNEXPECTED INCONSISTENCY, RUN FSCK MANUALLY". If i run "fsck /dev/sda2" it works,but why? [closed]

i had an error at Ubuntu 17.04 before booting. It said: "UNEXPECTED INCONSISTENCY, RUN FSCK MANUALLY" . So i typed after finding the problem's