Feature Complete Out-of-the-box
TYPO3 is unique in the quantity and quality of features that are part of its core. While there are over 6.000 extensions in the official TYPO3 Extension Repository, the following features are present without installing any community-developed extension.
No Frontend Design Constraints
Because the TYPO3 frontend and backend are separate and distinct interfaces, developers have complete and total control of their frontend markup, CSS, and JavaScript, down to the most minute details.
Frontend Editing
While the backend offers complete control over all site content, TYPO3 also includes a frontend editing interface for even faster, more intuitive content management by non-technical editors.
Enterprise Features
In addition to everything one would expect in a sophisticated content management system, TYPO3 also possesses a number of important enterprise features including content-specific caching backends, a database abstraction layer, documented serviced-based APIs for authentication like LDAP and Active Directory, well-defined interfaces for third-party systems integration, reporting tools, a digital asset manager, and an interface for scheduled jobs.
And More...
For a full list of all that the TYPO3 core has to offer, take a look at the feature matrix on typo3.org. Or browse the list of over 6.000 extensions on the TYPO3 extension repository.