Setting Site Information
"Site information" refers to the name, slogan, mission statement, and footer messages that appear on your site, as well as the default front page, the email address your site uses for automated notices, and the name it gives anonymous visitors. All of these settings appear on one convenient form:
Navigation menu » Administer » Site configuration » Site information
You can set your site's name, slogan, etc. on the Site information form, but whether and where they appear also depends on your site's Theme. A Theme is a set of files that determine the overall graphic appearance of the site. Your Theme will set where the name and slogan appear, for example – or it may let you choose whether or not to have the slogan appear, or it may not be capable of displaying the slogan at all.
In other words, the basic appearance of your site is largely determined by 1) the information you input here in Site information, and 2) the site's Theme. See more at Configuring Your Theme.
Filling in site information
Here are the fields on this form:
The name of your site.
Input an address that your site will use for automatic notifications, password requests, and so on. This should be an address that the chief site administrator checks often.
If your site's name is its title, its slogan is like a sub-title. Use this field for a short description of the site, or any slogan or message you want to appear alongside the site name.
If the site slogan is like a sub-title, the mission statement is like a sub-sub-title. Input something here if you'd like yet another identifying or greeting message. With many themes, the mission statement will appear not in the site's header, but at the top of main content, and only on the front page.
A message that appears at the bottom of the site. This is traditionally used to note the site's designer or developer.
This item seems a bit out of place on this page, but there it is anyway. Your site needs to place some name on anonymous visitors – for example, in logs that note visitors, or in comments if you allow anonymous visitors to leave comments. Here you can set what you like. "Anonymous" or "Visitor" are common, bland choices. Some sites use more interesting names (like those that place the label "Anonymous Coward" on visitors who leave comments without registering for an actual user name). It's all up to you.
Default front page
You can conveniently set any page within your site as the front page that a visitor will see when heading to your site. For example, if you've created a page with the address <your domain URL>/special_sale and would like that page to greet all visitors, input special_sale here.
See more here: Setting the Front Page