How a thesis is structured is not the same thing as how it is formatted.
STRUCTURE refers to the intellectual arrangement of the thesis. A useful analogy is a cookbook cake recipe. Typically, a cake recipe is structured in the same way.
Cake Recipe Model
A thesis follows a standardized academic structure.
The End of Program Assessment Manual for Graduate Studies outlines the structure requirements for the thesis/capstone paper.
FORMAT refers to the visual presentation/layout of the thesis, such as margins, line spacing, etc.
Using the cake analogy again. You can use a single recipe to make the same cake, but you can decorate it differently. That is, you can use different styles of decoration.
Academic papers have a required format, or editorial style. The "decoration" or format instructions are found in style guides.
The purpose of a style guide is to provide uniformity in writing and documentation/ citation styles and in formatting a document. Following a standard guide ensures that your paper is professional-looking and readable. Journal publishers typically require authors to follow a specific style guide, so it is a useful skill to know how to use one!
Learn to distinguish between scholarly and popular articles in this video by Vanderbilt's Peabody Library.