The My Today page gives you an overview of your entire account.
Calendar - lists upcomming events on your calendar.
Latest RSS Items - list recent updates to RSS feeds you are subscribed to.
Inbox - lists how many unread messages you have.
Disk Space Limits - lists how much space is available and how much space is being used in your account. Press the "Clear Junk E-Mail Folder" link to remove all items from your Junk e-mail box.
Tasks - lists unfinished tasks.
The My Today page is the default page to load when logging into your account. If you would rather go straight to your Inbox you can change it by going to Settings|My Settings|WebMail and changing the "Initial Page on Login" setting.
