A changelog is an essential tool for software companies to document and share updates made to their product, providing historical context and keeping customers informed of new changes. It serves as a centralized location to share concise updates with customers, promoting transparency and customer support, while also showcasing the growth and progression of a brand's product. The best format for a changelog depends on the target audience, but common practices include being concise, including key details such as date, change description, benefits, and next steps, linking to more detailed release notes, using visuals like gifs, and maintaining consistency. By having a changelog, software businesses can provide clarity around their product evolution and make it easier for users to find the information they need.