In the past, you'd need to install SDKs on your own, then visit the Preferences panel and point ADT to the root install folder - and you'd find out about it when trying to use a feature depending on SDK information.

Now, we ask you the first time you start Eclipse after installing ADT, to get everything set up once and for all.

Instead of just asking you where the SDK folder is, the wizard also offers to actually install some SDKs to get started. It offers you two options (and you can choose both): install the latest and greatest to be able to use the latest APIs and features, or install a baseline version to support a large majority of users. When you finish the wizard, it runs through the SDK manager in a special mode to download and install the chosen SDKs.

Here's the second page in the welcome wizard:

This page asks whether you're willing to contribute usage statistics. In the past, this was done as a separate dialog which would sometimes compete for focus with other windows, so now we'll get the question out of the way once and for all as part of the setup flow.