Whats new in drupal7?

Usablity

1.Better User Interface for administrator sine there is page loading instead they have user dialog box.

2.Dashboard Menu introduced so that administrator which have important content in that dashboard eg. who's online,List Recent post so that administrator can approve which is configurable.

3.CCKS,Image cache & Url alias module is inbuilt in drupal7

4.They have changed the title of some of the administrator Configuration

5.All the files used in an module folder must be defined in info file

6.More secure implementation for scheduled tasks (cron.php).

Database

1.Added query builders for INSERT, UPDATE, DELETE, MERGE, and SELECT queries.
Support for master/slave replication, transactions, multi-insert queries,delayed inserts, and other features.

2.Added support for the SQLite database engine.

3.Default to InnoDB engine, rather than MyISAM, on MySQL when available for greater scalability and data integrity.

JavaScript changes

1.Upgraded the core JavaScript library to jQuery version 1.4.2.

2.Upgraded the jQuery Forms library to 2.36.

3.Added jQuery UI 1.8, which allows improvements to Drupal's user experience.

Why is drupal is widely used for cms?

Use Drupal to build everything from personal blogs to enterprise applications. Thousands of add-on modules and designs let you build any site you can imagine.

Drupal is free, flexible, robust and constantly being improved by hundreds of thousands of passionate people from all over the world.