From: https://en.wikipedia.org/wiki/S.M.A.R.T.
S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology; often written as SMART) is a monitoring system included in computer hard disk drives (HDDs), solid-state drives (SSDs),[1] and eMMC drives. Its primary function is to detect and report various indicators of drive reliability with the intent of anticipating imminent hardware failures.
So, your computer's disk-drive is "failing", and needs to be replaced, as soon as possible.
Any attempts to "repair" it may prevent you from recovering any of your personal files.