userdir is the directory where NetBeans stores user configuration data such as window layouts, editor settings, menu and toolbar customizations and various module settings.
Per default, it is a (hidden) directory called .netbeans stored in the user's home directory. The home directory is (=${HOME}= on Unix-like systems, C:\Documents and Settings\<user> on Windows) under .netbeans/<nb-version>. As the name suggests, userdir is unique per user.
Modules can use userdir to store persistent data (for example, source and library file databases and indexes). Also, additional modules installed by the user are typically stored in the userdir.
To find out the exact userdir location go to the main menu, invoke the NetBeans | About NetBeans.
Applies to: NetBeans 3.6, 4.0, 4.1, 5.0, 5.5, 5.5.1, 6.0
Platforms: All