Every website has a purpose. If you don't know what the purpose of your website is, you need to figure it out before you write your content. Each page needs to have a goal and the content must be written in such a way that it helps you achieve that goal. There are many different actions users can take when they visit a website, and your copy should steer towards the action you want them to take.
If you have a website that sells products, you want your website visitors to buy something. How do you get them to do that? First of all, you give them the information they need to make a decision. You tell them all about the product, describing all of its features, and perhaps even using a video to demonstrate how it is used. Then you need a call to action. Tell them what they need to do to place an order and make it easy for them to do so.