ROI = Return on Investment
ROIC = Return on Investment Capital (also known in some circles as return on capital)
Both of these are measures of a companies performance, but they differ in scope. ROI refers to the efficiency of an investment’s ability to generate a gain / loss (hopefully it is a gain or you wouldn’t undertake it) and ROIC is a measure of literally how efficiently a company is using its resources (money) to generate more resources (money).
Equations for each:
ROI = (Gain on Investment - Cost of Investment) / (Cost of Investment)
ROIC = (Net Operating Income - Dividends) / (Total Capital)
They are very similar in that they both determine the efficiency of an enterprise, however ROIC determines the efficiency of the whole company, while ROI only determines the efficiency of one particular investment.