The Description and Explanation of the Research Process is the most important piece of your submission and carries more points than any other application component, including the project itself. In 800-1000 words you will describe, in detail, which library resources you used, how you searched them, how you improved your search strategies, how you evaluated the sources you found, etc.
A research log is a record of precisely these sorts of search process details. You might keep track of when you searched, where (which database for example), what keywords you used and how you combined them, the number of results, notes about new keywords you discovered in your search results, and other details. When it comes time to describe your research process you will have all the information you need in your research log.
Below is a Google Sheets research log template that you may use and modify as you wish. Click on File, Make a Copy, then save to your Google Drive.