Remediation has to do with righting a wrong or correcting a fault. Students who can't read well or do their multiplication tables might need remediation to bring them up to speed.
Remediation is a word for fixing things that aren't right. You often hear about criminals needing rehabilitation, which is close to remediation: after remediation, you're a better or smarter person. Students who get to college but aren't quite ready for college work need remediation. In all forms of remediation, the idea is you're going to help people get better in some way.