The following text is taken from Wikipedia.
Impact investments are investments made into companies, organizations, and funds with the intention to generate measurable social and environmental impact alongside a financial return. Impact investments can be made in both emerging and developed markets, and target a range of returns from below market to market rate, depending upon the circumstances. Impact investors actively seek to place capital in businesses and funds that can harness the positive power of enterprise.
Impact investing occurs across asset classes, for example private equity / venture capital, debt, and fixed income.
Impact investors are primarily distinguished by their intention to address social and environmental challenges through their deployment of capital. For example, criteria to evaluate social and/or environmental performance are an integrated component of the investment process.