What template file is used by default for posts?

You can create new template php file.

//Template Name : Single Page Template
get_header();
if ( have_posts() ) : 
     while ( have_posts() ) : the_post(); 
         the_content(); 
         the_permalink();//this is for the <a> bunch you are looking for
     endwhile; 
endif;
get_footer();

Here , you can use “//” or “/** **/” to set the Template name , it varies from the theme you are using.
and then , go to Add New Page and there on the right sidebar , you can choose this template , by default it was set “Default Template”.
There on dropdown , you can find the newly created template file named “Single Page Template”.