Concept of "sawab" according to Quran and hadith

I have been told that sawab is a unit of "naiki". It will be something that will be counted or weighed on the Judgement Day. Is this concept supported by Quran and hadith? Specifically, as a unit of measuring good deeds. If not, what is the concept of "sawab" according to Quran and hadith? Based on my search in quran , it is used in meaning of "reward" or "recompense", which can be both good or bad