How would we know, what kind of breadcrumb we are using in our portal

Question

I am bit confused with Navigation in SharePoint, I looked at web.config and then site map, which is enabled and have several tags of "

• If we have a default NavigationProvider and a Custom NavigationProvider can we use both of them in 1 portal.
• How does BreadCrumb Navigation works in SharePoint I mean if its enabled by default in SharePoint 2007 or do we have to enable it in "SiteMap" element and then add anything to our Custom Master Page.
• How does Custom BreadCrumb Navigation works in SharePoint, e.g. if I want to create a user control that gets data from Database and adding it to a custom master page, is thats all gonna make it work ?

Thanks a lot for your Time.

Cheers