Placeholder images are temporary graphics used in design and development to represent where an actual image will go. They help designers visualize the layout of a webpage or app without needing the final images ready. These images often have a simple design, like a gray box or a blurred photo, making it clear that they are not the final product. Using placeholder images can speed up the design process, allowing teams to focus on other elements like text and functionality. They are especially useful in projects involving web design, mobile apps, or graphic design, where the final visuals may not be available yet.