The day view is set up to look a bit like a website, and just gives you a bit of detail about the day.
It shows:
Entry's titles appear as links, and if you click on that link, that item will become the selected item in the Item View.
If you click on a link using the right hand button, it will show you a popup menu of common actions that you can perform on that item.
You can switch to look at different days using the Calendar menu.