There is a setting in the Joomla site configuration, which is often overlooked or used to hold allmost nothing, in best case the URL of the site, the Site Name. You're asked during the install to fill the respective field, and you generally have no clue what to write in that box.
So, what's wrong with that? The site is working, regardless what you wrote there...
You may think one can wrote here anything crosses his mind, right?
Yes and no. To get high ranking on search engines, and, of course, high visibility of your pages on the Net will become sooner or later a priority of any webmaster. And, generally, they need to open their vallet to obtain this. Hiring a good SEO pro isn't cheap or easy, so why you don't try to do as much from the SEO wizardry yourself?
Let's begin with the very beginning: What's your URL/domain name? Also generally overlooked, this is a key factor in your further success.
But, when you read this, you probably already have one, then let's go to the next thing your visitor - and the search engines - are seeing from your page.
Yes, the TITLE of your web page (Sitename in the Joomla language). This is the important, probably the most important part of a page contributing to a good ranking in search engines like Google and Yahoo and should ideally be optimized for a small number of keywords or phrases (your main targets, of course, preferably just the main marketing phrase for your page). The exact number of keywords used and their placement is dependent on a number of SEO factors including the difficulty of the phrases - obviously you need to find a good balance here between the humanly readable, acceptable title and one rich in your targeted keywords - , the actual and targeted Page Rank of the page and the fact if you have or not some control of the links and anchor text to that page (so you can change at least in some cases the anchor text of the links). All of these are contributing to the success of your site.
A well chosen page title (Site Name) sells itself, and can contribute a lot to your final success.
So, take your time, and choose a good name for your site!