{pad}...{/pad} is the plainest tag there is: it returns TRUE and does nothing else, so its content renders once. It exists as a carrier for what every tag can do - data=, content=, name=, level variables, pipes, the handling options and properties - on a tag that adds no meaning of its own.

With data='store' the content repeats once per row of that data, and name= gives the level a name for its properties: {current@rows}. Variables assigned on the tag - {pad $who = 'world'} - exist inside it and are gone after the closing tag. A pipe on the closing tag, {/pad | upper}, works on the whole rendered content.

pad is also what the pad: type prefix names: {pad:if} is the built-in {if} even where the application has a tag of that name. A {pad} is the natural wrapper when a block of template needs options but no data tag fits.