
Domain name registration is the act of staking out "mycompanyname.com" or something similar as your own. 
Domain name registration prices vary, but should be $35 per year or less (the best deals are much lower, but read the fine print; make sure you will legally own your domain name).
godaddy.com is one of the cheapest domain name registrars available. GoDaddy will strongly encourage you to purchase your web hosting service from them as well. And there's nothing wrong with their web hosting service. But keep in mind that you do not have to registration and web hosting from the same company.
Many web hosting companies can handle domain name registration for you in order to speed things along. They often offer the best deals on registration because they are counting on you to sign up as a hosting customer as well.
A "hit" to a web site means that the server was accessed to retrieve a file. That file can be an .html file, an image file, an audio file, a Java applet, CSS file, .js file--anything that is connected to a web page. Each time the server is queried, that is, each time a file is requested, that is considered a "hit."
As you can tell, a single web page can cause many "hits" as the page is downloaded. A "visit," otherwise known as a "pageview" is just that...the user requests a web page and that page, including all it's associated files, is downloaded to the user's machine.
You can see that the number of pageviews is more significant than the number of hits.
The easiest method is to use what's known as the .htaccess file to restrict access to your site. You can find more info about the .htaccess file in this article:
http://webdeveloper.internet.com/servers/servers_htaccess_magic.html
Essentially, the .htaccess file allows you to restrict access based on IP address or domain. This can be done by yourself if you have access, or it may have to be done by your web host if you do not