Directory structure

The files that make up SeltzerCRM are organized as follows:

/ - root directory, license, readme, etc.
  crm/ - The root path of the web app and front-end php files
    config.inc.php - The configuration file
    include/ - The php files that make up the web app
      sys/ - Core subsystems to be used by all modules
      crm.inc.php - A central include that includes the rest of the web app
    install.php - main install script used on first run
    modules/ - directory for all the modules
      amazon_payment/ - amazon payments integration into billing & payments
      billing/ - allows calculating of membership dues
      contact/ - the main data object which seltzer is built around
      core/ - The core module code
      devel/ - module containing development & debugging tools (disabled by default)
      key/ - allows for the tracking of RFID keys & assigning them to users (disabled by default)
      member/ - allows for administration of plans and assigning users to plans
      mentor/ - allows the assigning of one member to another as a mentor/protege pair (disabled by default)
      payment/ - allows the recording of payments towards membership dues
      paypal_payment/ - paypal integration into billing & payments (disabled by default)
      plan_meta/ - allows the assigning of arbitrary meta data to plans (disabled by default)
      profile_picture - allows the user to assign a profile picture using gravatar (disabled by default)
      user/ - handles core login/log-out/(re)setting of passwords
      user_meta/ - allows the assigning of arbitrary meta data to users (disabled by default)
      variable/ - catch-all module used to store strings
    themes/ - different js & css themes (only 1 currently, default "inspire")

Most of the time you will only need to modify config.inc.php to set up system wide config options, and edit files & folders in the modules directory