A filler, or placeholder, is a temporary element used in design, writing, or programming to indicate where content will eventually be placed. It helps to visualize the layout or structure before the final content is ready. Common examples include Lorem Ipsum text in graphic design or empty boxes in web development. Fillers are useful for maintaining the flow of a project, allowing creators to focus on layout and functionality without getting distracted by the specifics of the content. They can be replaced with actual content later, ensuring that the overall design remains intact during the development process.