Abstract and summary are equivalent to the outline of a paper, and the content you wrote and the purpose of the paper can be reflected in the abstract. Many teachers will not read all the contents of your paper bit by bit when marking papers, but they may decide the quality of your paper by reading your abstracts and summaries. Just like the English composition test, a teacher can't read thousands of articles sentence by sentence in one hour, just looking at the first few sentences and the last ending. If you write well, you will get high marks, and so will your thesis.