Check out this article by Neil Gregory at IFC - International Finance Corporation and Kusi Hornberger at Dalberg.
How is Environmental, Social & Governance (ESG) investing different from impact investing?
There are 3 key requirements of investors to ensure their investments are impact investments and not ESG:
1) Selection of assets with intent for impact
2) A contribution to the impact of the investee firm
3) Objective measurement of that impact
These practices, enshrined in the Operating Principles for Impact Management, are what ensure that investments make a real, positive impact, and help the market avoid ‘impact washing.’