The back matter of a thesis should include an abstract, acknowledgements, a list of references, and appendices (if any).
An abstract is a brief summary of the thesis, typically ranging from 150-250 words. It should be written in a clear and concise manner, and should include the research question, methodology, results, and conclusion.
Acknowledgements are a way of thanking those who have helped you during the research and writing process. This could include your supervisor, collaborators, colleagues, or friends.
A list of references should include all the sources that you have used in your thesis. This includes books, articles, websites, etc. The format of this will depend on the citation style you are using (e.g. APA, MLA, Chicago, etc.), so be sure to check the style guide for guidance.
Appendices are any additional materials that are relevant to the thesis but are not essential for the main text. Examples could include data sets, detailed calculations, or maps.