To choose which format you want to use on which sheet, choose either File > Page Setup or double click on the sheet size at the bottom of the Graphics Area.
A format typically contains graphical entities for the border of your sheet (e.g., zones) and tables with parameters (that's the fill in the blank information). You can create your own formats from the File > New dialog box.
A template typically contains a format and does a lot of things for you automatically, like placing views, dimensions, balloons, etc. onto your drawing. You create a template by starting with a drawing and choosing Applications > Template.