When page template designers creates a page template, one of their main tasks is to define placeholders for the template. Placeholders reserve areas on the page into which content authors will add their specific content. Placeholders are defined as a particular type, which controls the type of content that can replace the placeholder when the template is used to create a page.
For example, a placeholder might be defined to contain an image, and the page template designer might put a temporary image into the placeholder. It is considered good practice to make the temporary image contain text such as "Place your photograph here," so that the author knows what type of image to put into that placeholder, and so that it will be easy for an editor to notice if the image is not replaced. Note that if the default Content Management Server image is left in the placeholder, it will never be shown on the live site, but it will also not serve to tell the author what type of image is supposed to be used.
Or a placeholder might be defined to contain unformatted text, and the page template designer might put the text, "Place the title of the article here," and then surround the placeholder with HTML formatting tags.