This document provides an overview and introduction to the SME Banking Knowledge Guide. It discusses how SMEs rely heavily on banks as their primary source of financial services and how banks are increasingly targeting the previously underserved SME market. The guide aims to share lessons from banks that have successfully engaged with SMEs, overcoming challenges like high credit risk. It focuses on the experience of commercial banks, which offer a broad range of financial products and services to formal sector SMEs. The introduction sets up an exploration of the current state of SME banking and approaches that banks are using to profitably serve small and medium enterprises.