In SharePoint 2007 it is possible to create site templates based on an existing site. A template can be used to create new site collections and subsites based on that template. When you export a site template, it creates a .stp file for you. Copying this .stp file over to an other evironment gives you the possibility to start using your template over there also.
In SharePoint 2010 site templates are still there. You can create site templates, but these are created as .wsp files instead of .stp files. This gives you the advantage of importing this .wsp into Visual Studio and make solutions based on it.
If you have a SharePoint 2007 Site Template, you cannot export it as a .stp file and import it into SharePoint 2010. The approach for getting your SharePoint 2007 Site Template into SharePoint 2010 is as follows:
- Setup a SharePoint 2007 environment
- Create a SharePoint 2007 site using the .STP site template
- Backup the SharePoint 2007 site
- Restore the SharePoint site into a SharePoint 2010 environment
- If needed update your site, so that it matches the SharePoint 2010 v4 masterpage and makes use of the new SharePoint 2010 features.
- Export your site into a new Site Template
Now you have your SharePoint 2007 Site Template converted into SharePoint 2010, so you can use it to make site collections and subsites based on that template.