Mockup:

In marketing, a mockup is typically used for promotional purposes. Mockups allow you to visualize a project. It is a great tool to present in a marketing pitch because it allows you to use visuals to describe your ideas. 

There are many forms of a mockup:

• Print
• Device
• Branding
• Packaging
• Product
• Social Media

Source

Here is an example of a website mockup. It shares what will go where and gives you a general idea of what it will look like.