This is often confusing to people who are new to Joomla. The thing to remember is that a Joomla site is really just a wrapper for your content.
When people (like us) create Joomla templates we put in content or use the standard Joomla demo data to create sites. We add logos to module areas etc and generally spend some time setting the site up to showcase the template.
Your install may not have the same content or graphics so will look different.
You may also find that the template is using a special menu system such as Sucker Fish and this needs to be added to Joomla separately from the template.
If you Google 'Joomla overview video' you will find a link to a YouTube video I created to provide an overview of the Joomla CMS, this might help.
Feel free to ask specific questions, we pretty much know Joomla inside out
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