PostgreSQL 13 presents a lot of changes: many of them will not be immediately visible to the user, while others will be available to administrators, and others still will be integrated into the command-line tools. Describing all the new features is almost impossible, because every new release includes a lot of human work, and that work goes into making PostgreSQL more stable, usable, and efficient.
Now, thanks to the knowledge you have gained throughout this whole book, you are able to install PostgreSQL 13 or even a higher version and go find the features you like the most and fit your needs best. Use this book as a teammate during your journey of exploring PostgreSQL, and feel free to jump back and forth between chapters depending on what aspect of PostgreSQL 13 you are learning about or faced with.