To have the theme listed:
style.css
With at minimum this:
/*
Theme Name: Minimum Theme
Description: Test
Author: Test
Version: 1.0
*/
For the theme to be functional:
index.php
index.php
must have a post loop, so this would be the bare minimum functional index.php
<html>
<head><?php wp_head(); ?></head>
<body>
<?php
if ( have_posts() ) {
while ( have_posts() ) {
the_post();
the_title( '<h3>', '</h3>' );
the_content();
}
}
wp_footer();
?>
</body>
</html>
index.php is the defacto fallback for all template files WordPress might look for. All the rest are entirely optional, though I advise that you use them.
For more information on which templates are possible, see here: