SEO File Names/URLs
The address of each page on your site is made up of two things. The domain of the page, and the path to the page withing your hosting.
Domains
On the Spanglefish system we normally create new sites on the domain www.spanglefish.com, or one of a handful of other domains we use which are targeted at specific sectors - eg www.parish-council.com.
So your new website will probably have an address something like
www.spanglefish.com/mywebsite/
where /mywebsite/ is the folder we put your website in on our domain.
It does help to have search terms in the site address, so for instance
www.spanglefish.com/redleathershoes/
would help you be found in search engines when someone searches for 'red leather shoes'.
Even better would be one of
www.redleathershoes.com
www.red-leather-shoes.com
You can register your own domain to use instead of the original Spanglefish address - see the Domains section of your Site Settings page.
File Names
The second part of your URL is the file name. When you first create a page on your website you'll find the system has given it an address something like
www.spanglefish.com/mywebsite/index.asp?pageid=123456
Clearly, this address doesn't really tell anyone what the page is about. So once you've created your pages go to Site Settings --> Search Engines etc --> Create Unique Page Addresses and change it to something like
www.spanglefish.com/mystuff.asp
Putting these together
If you have your own domain then you have the ability to create perfect URLs for your pages. So for instance you might have the URL
www.red-leather-shoes.com/girls-tap-dancing-shoes.asp
If your page really is about red leather girls tap dancing shoes, and you've tailored your text, page title and meta tags, then you've given yourself a really good chance of being found on Google next time someone searches for 'red tap dancing shoes for girls'.