The document discusses several new features in MySQL 8 including:
1. A new data dictionary that stores metadata internally instead of external files, allowing for transactional ALTER TABLE commands.
2. Support for common table expressions and windowing functions.
3. Improvements to the optimizer including index and join order hints, descending indexes, and optimizer trace output providing more details.
4. Support for roles which are named collections of privileges that can be assigned to users.
5. UTF8MB4 is now the default character set providing support for emoji and supplementary characters.
6. Ability to create invisible indexes that are not used by the optimizer but are maintained for testing performance impact.