www.x.com is pointing to my site on my server (x is an example) www.x.wordpress.com is pointing to an old blog. please someone explain how the . in domain names works, is it a folder on the server? do i add on the domain?
It's a subdomain. Like you have http://forums.digitalpoint.com where forums is the subdomain and digitalpoint is the main domain. You can configure this in your control pannel (like cPanel). - Aquarezz
The dot operator is used to denote Sub domains In www.x.wordpress.com, x is a sub domain of wordpress.com
actually is the full address, now freefor15.com is hosted on my server, but freefor15.wordpress.com is pointing to an old blog not on my server anymore. when i try to add freefor15.wordpress.com in add on domains in cpanel says its not valid
You cannot delete/control freefor15.wordpress.com since its not owned by you though freefor15.com is yours... freefor15.wordpress.com is a blog hosted by someone else at www.wordpress.com Its in no way related to you or your server...
In cpanel,you will find an icon called subdomains. just click it and in the next page,you'll find two text boxes(the second box will contain your domain name) enter "blog" in the first text box and click the create button now you can upload your files to /public_html/freefor15.com/blog/