What is Eclipse??
"Eclipse is an open source community whose projects are focused on building an open development platform comprised of extensible frameworks, tools and runtimes for building, deploying and managing software across the lifecycle. A large and vibrant ecosystem of major technology vendors, innovative start-ups, universities, research institutions and individuals extend, complement and support the Eclipse platform. New to Eclipse?"
Is it free??
Yes, totally :) .
What is it used for?
Embedded + Device Development
Rich Client Platform
Where can I download the newest release??
and choose the package you need.