This site is about Adobe Flex and Flash, offering free tutorials on Flex application development.
Flex is a development environment for producing Flash Applications. It is currently sold as Flash Builder and is at version 4.5. You can get a trial version of Flash Builder at the Adobe website and if you are a teacher or a student in a recognised institution you can get a free license for it.
Alternatively, you can download the open source Flex 4.5 Software Development Kit for no charge at all, although it is slightly more difficult to use.