main.tex is the LaTeX source for the report. main_preview.pdf is a pre-built PDF if you just want to read it without compiling anything.
To build it yourself (requires a LaTeX distribution, e.g. TeX Live or MiKTeX):
pdflatex main.tex
pdflatex main.tex # run twice for cross-references/TOC to resolve
Figures referenced by the report live in figures/.