The content of a site is its information (what users can learn from the site) and functionality (what users can do with the site). It is the most important factor that determines whether a site is useful or not.
When you plan content for a site, it can be helpful to consider the different types of people who will visit the site. You can ensure that your content is relevant to each group of people.
The content should be logically organised into sections (or some other approprite structure). You can organise it based on the different types of user, or based on the content itself. The organisation should be clear so that users can understand both where they are in the site, and where the information they are looking for will most likely be located.