A template's format is the overall wireframe, providing layout structure for where headers, content, sidebars, and footers are located. It is also where CSS code is stored. In terms of building a template, everything is stored in your format: sections, blocks, and slots.
The below code demonstrates a complete format, albeit with only a single block.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> </head> <body> <table width="100%" border="0" cellspacing="0" cellpadding="0" id="snt-document" class="mobilewrapper"><!--wrapper--> <tr> <td align="center" valign="top"> <!--SectionStart width="600"--> <!--BlockStart name="2.2 Header Logo Left" width="600"--> <table id="snt-content-header" class="mobile100pc" border="0" cellspacing="0" cellpadding="0"> <tr> <td colspan="3" class="snt-col-h"></td> </tr> <tr> <td class="snt-colsplit" align="center" valign="top"> <!--SlotStart type="ImageOnly" maxwidth="275"--> <img src="http://placehold.it/275x140" /> <!--SlotFinish--> </td> <td class="splitspacerHeader"></td> <td class="snt-colsplit" align="center" valign="middle"> <table class="table2col" border="0" cellspacing="0" cellpadding="0"> <tr> <td colspan="3" class="snt-col-h"></td> </tr> <tr> <td class="snt-col-w"></td> <td class="snt-text-slot logotext"> <!--SlotStart--> <h3>This is an H3</h3> <p>This is a paragraph. Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p> <!--SlotFinish--> </td> <td class="snt-col-w"></td> </tr> <tr> <td class="snt-col-h" colspan="3"></td> </tr> </table> </td> </tr> <tr> <td colspan="2" class="snt-col-h"></td> </tr> </table> <!--BlockFinish--> <!--SectionFinish--> </td> </tr> </table> </body> </html>