Answer
to record any information that might help you with the research process
Explanation
A writer's journal is a tool to unload your toughs and record everything that you consider useful in your writing process (facts, opinions, dates, styles,..). The idea is to get the ideas out of your head and the facts onto the paper so you can later crystallize the information. In that sense, you could said that a writer's journal is the main tool to record any information that might help you with the research process.
