Admin Panel → Dashboard
By default, the Dashboard is the first page you will view when logging in to the admin. The Reports offer more detailed information about your store and sales, you can get a quick view of some of the most important information regarding your site through the Magento Admin Dashboard.
In the top left corner is the View Statistics for drop-down, where, like most reports, you can change the scope of the data represented. In the left column is a summary of your Lifetime Sales (total monetary amount of all Orders) and Average Sales (total monetary amount divided by number of Orders), followed by links to the five most recently placed Orders, five Search Terms most recently used in the front-end, and five most popular Search Terms (based on number of uses).
In the main section of the Dashboard, in the Orders tab, you can see a chart of Order frequency over a period of time, which you can change in the Select Range drop-down. If you select the Amounts tab, it will display the same information using the monetary amounts of the various Orders, rather than the number of Orders placed. At the bottom of this chart is the Revenue (total monetary amount of all Orders), Tax (total monetary amount of all Taxes paid), Shipping (total monetary amount of all Shipping paid), and Quantity (total number of all Orders placed).
Underneath this section are four tabs, each containing links to various pages of the admin. The Bestsellers tab contains links to the five most purchased products. The Most Viewed Products tab contains links to the five most viewed products. The New Customers tab contains links to the five most recently created customer accounts. Finally, the Customers tab contains links to the five customers with the highest Total Order Amount.
If you do not want the Dashboard to be the first page after logging in, you can set Magento to go to any other page instead via System → Configuration → Admin tab → Startup Page panel.