I'll let Google do the talking:
Wow. Too cool. This will really energize developers and end users alike to get behind Android. The momentum is really building now!
[The] Android Market [is]an open content distribution system that will help end users find, purchase, download and install various types of content on their Android-powered devices. The concept is simple: leverage Google's expertise in infrastructure, search and relevance to connect users with content created by developers like you.
Developers will be able to make their content available on an open service hosted by Google that features a feedback and rating system similar to YouTube. We chose the term "market" rather than "store" because we feel that developers should have an open and unobstructed environment to make their content available. Similar to YouTube, content can debut in the marketplace after only three simple steps: register as a merchant, upload and describe your content and publish it. We also intend to provide developers with a useful dashboard and analytics to help drive their business and ultimately improve their offerings.
I also wanted to share some early details to help with planning your efforts so that you can be ready as our partners release the first Android-powered handsets. Developers can expect the first handsets to be enabled with a beta version of Android Market. Some decisions are still being made, but at a minimum you can expect support for free (unpaid) applications. Soon after launch an update will be provided that supports download of paid content and more features such as versioning, multiple device profile support, analytics, etc.
One glaring omission worth noting is security. With no approval process for the applications, any malicious code may find its way into the Android Market and eventually onto end-user devices. I would hope that "security" is one of the decisions that Google alludes to not having been made yet.
What about it, Google?