It clarifies the structure of your thesis and helps you find the correct focus for your work.
But this is also why working on your summary can be so useful – it forces you to identify the key elements of your writing project.
There are usually no formal requirements for forewords, but it is common practice to thank your supervisors, informants, and others who have helped and supported you.
It should make a good impression and convince the reader why the theme is important and your approach relevant. What is considered a relevant background depends on your field and its traditions.
Background information might be historical in nature, or it might refer to previous research or practical considerations.