Help reading S.M.A.R.T info

[Appleboy45]

I'm trying to learn how to read S.M.A.R.T info on hard drives. I recently got this HP laptop out of recycling to see if I would find it useful at all or if it has good parts. I pulled the hard drive out and put it in an external hard drive and plugged it into another computer with CrystalDiskInfo. I got a caution message and both of the attributes reallocated sectors count and current pending sector coconut are yellow. I don't have anything important on the hard drive so I don't care if it fails or not. My question is, what do the current, worst, threshold, and raw values mean? Can these tell me how many errors there are?