The GATE Compendium will be one of your most important tools throughout the game. It is important that you’re reading the entries in here. I would also suggest reading the emails because they give important lore and navigational context.

The compendium is broken down like this: 

• Soup Recipes: As you get more ingredients, the “?” icon will go away, and it will make it easier to make soup. Some soups have multiple portions. Soup Recipes can also be used to make things that are not food-related. You’ll need a soup bowl to eat your soup. 
• E-Mail: You can go back and click on any e-mail you’ve read. It is important to read the computer and click on the attachments! Some will even give you new crafting recipes. 
• Fish: All of the fish you catch are stored here. 
• Registry: The Registry contains information for things such as the Pest, those little enemies you’ll be fighting early on. Be sure to click on these and read them because they show key information about what a creature is weak to, what’s strong against it, and how it behaves. 
• Entities: Similar to the Registry, the Entities section provides important context for the various Entities in the game. It will also tell you what’s weak to what and what’s strong against what. 
• People: Contains all of the information you need to know about a given character. 
• Locations: Contains key information about the various GATE locations. Lots of lore and information are found here. 
• Theories: This is where your fishing tutorial, information about the weather events, and other theories live. You get these when weather events happen, the first time you make a fishing rod, and through other methods. 

So to summarize. 

• The GATE Compendium is where the Fishing and Weather events live. Be sure to read about them. 
• It contains information about weaknesses and also what weapons are best to use against which species. 
• Contains lore that provides context and will help you navigate the world and its creatures.