Google's Inbox experiment is about more than just email. Now, Inbox will collect all your emails related to a Calendar event into one bundle. You can also save links from around the web to your Inbox. Plus, it pulls out stories from newsletter emails. The new calendar bundle works a lot like Trip bundles do now. Any email you've received that relates to a specific Google Calendar event will be grouped together, for easy access.
The newsletter feature surfaces stories from the newsletters you subscribe to (like the Lifehacker newsletter!) so you can see at a glance which stories are worth reading.
Finally, Google has introduced a new extension (again) called Save to Inbox. This button allows you to save a link from the web as an item in Inbox. Since Inbox treats your email much more like a to-do list, this makes sense. You can already add reminders that you need to deal with later, and now you can save an important link so you remember to do something with it later.