Alternative investment funds (AIFs) are increasingly turning to credit markets through bond issuance, net asset value facilities, capital call facilities, and subscription lines. This activity in private markets reflects the slowdown in traditional fundraising and weaker deal activity, among other dynamics. As investors allocate increasing amounts of capital across the private debt markets, evolving macro and financial conditions may necessitate a need for greater transparency. This primer explains how S&P Global Ratings applies its AIF methodology to various fund structures across private equity, public equity, venture capital, and private debt funds, and alongside hedge funds and some investment companies that share key characteristics of AIFs. Our primer also details how we calculate stressed leverage for different types of funds, how we capture the risks relating to the funding and liquidity of different fund structures, and how we rate instruments issued by AIFs.