A “single-entry” Template simply means one where you have the URL Title or Entry ID specified in the URL.  In other words, you’re explicitly telling EE to display a single, specific entry.

Single Entry URL

- http://www.example.com/index.php/weblog/comments/147/
- http://www.example.com/index.php/weblog/comments/my_entry_title/
- http://www.example.com/index.php/weblog/comments/my_entry_title/P2/
- http://www.example.com/index.php/weblog/another_entry_title_here/

NOT a Single Entry URL

- http://www.example.com/index.php/weblog/comments/
- http://www.example.com/index.php/weblog/categories/C13/
- http://www.example.com/index.php/weblog/P5/