From b2evolution manual
This manual page is outdated. NEW PAGE: Introducing Templates in b2evolution v5+.
//This man page refers to b2evolution version: 0.9.0//
 Where are the template files?
A stub file actually just sets a few parameters and then lets b2evolution call the appropriate skin.
Skin templates are located in the folder /blogs/skins/ . This folder contains one subfolder for each installed evoSkin. You can add or delete evoSkins by adding or deleting folders there.
Each skin folder then contains at least one file name ((MainTemplate|_main.php)). This is the main template that is used when this particular skin is displayed.
Alternatively, if you are *not* using evoSkins, the stub and the _main.php template will be combined into a single file. This is how many low-end blogtools work. This is how Cafelog/b2 used to work. An example of such a file is provided as a_noskin.php .
The main templates indeed call sub-templates for specific tasks. These are located in the /blogs/skins folder and its subfolders (However, the subfolders are only used when using evoSkins). These are the commonly used sub-templates:
- _arcdir.php : displays the archive directory for a blog
- _archives.php : displays the archives list for a blog
- _bloglist.php : displays the list of available blogs
- _blogroll.php : displays the blogroll for a blog
- _calendar.php : displays the calendar to navigate through a blog
- _feedback.php : displays the feedback for a post
- _lastcomments.php : displays the last comments for a blog
- _profile.php : displays the user profile editing form
- _stats.php : displays viewing stats for a blog
Note: to avoid duplication of identical code, some skins will call the default sub-templates located in the /blogs folder instead of carrying identical sub-templates in their own subfolder.
 Special templates
The file /blogs/multiblogs.php for example, is an advanced template displaying several blogs at once. There is no skin equivalent for this kind of template.
 How do I edit the templates
Template files are .PHP file. These are very much like .HTML files except they contain PHP statements in order to display dynamic information out of b2evolution.
Any PHP information is enclosed in <?php and ?> tags. Be extremely careful not to delete these, or if you delete a whole block, make sure you delete the pair of tags.
You can edit the templates with a PHP aware HTML editor. For example, Dreamweaver will do fine but it is strongly recommended you use code view to watch closely what you're doing.
Check out the TemplateFunctions to understand what's between the <?php and ?> tags.
Please also note that most templates and skins make use of CSS style sheets. The actual styles can be found in .CSS files and can be edited with a style editor.
Anyway, all those files can be edited with a text editor like notepad, although it is highly recommended you use an editor doing syntax coloring instead!
It is recommended you start by customizing the custom skin (/blogs/skins/custom/)
 Why do some files start with an underscore (_) ?
The underscore is a convention indicating that this file is not to be called directly from the web by its URL. Instead, this file is only to be included by another file.