What does that mean?

It means that Beadle & Grimm have taken that heap of books, character sheets, and journals stacked up in front of you at the table and distill it down into one book that contains:

• 20+ page character sheet. Everything you need at your fingertips, including plenty of room for home-brew rules, familiars, allies and enemies, and more.
• All the rules from the Pathfinder 2e Core Rulebook and Advanced Player Guide that you need to run your character, and only your character.
• A journal for you to record your character's entire story.