Q:

What is the use of mod_dav_svn.so? 

While integrating the apache and the subversion, we are using mod_dav_svn.so and loading this module, can any one help me to know the use of this module? 

A:

Roughly speaking, it's a module which allows Apache HTTP Server to serve SVN repositories. 
See WebDAV FAQ: "What is mod_dav_svn and mod_dav_fs?" 

mod_dav_svn is an interface for mod_dav that provides a CVS like
  repository which is based on the new Delta-V specification.  It is an
  extension to WebDAV and useful if you need versioning control. 

and SVNBook | httpd, the Apache HTTP Server.