Thank you Adrian. That clears things up. I'm not really a php programmer but want to learn it well enough to set up a template. I'm a .net dev and the idea of omitting a closing tag seemed odd to me. How does ProcessWire know to include the _ files. Is it defined somewhere in the admin?
I just installed ProcessWire for the first time and I've perused the documentation but haven't seen an explanation of the template files that start with an _. Can someone explain to me how those work? Also, how come they have an opening php tag but no closing tag? Is there anything that explains this in depth?