The Rational ClearCase actions provide an interface via Rational's Cleartool. Each action wraps almost all the functionality of the relevant cleartool command. For unsupported commands, there is a generic Cleartool interface which allows Cleartool to be called directly.
Default View Location allows you to specify a "view context" directory to be used as the default for all ClearCase actions which use a view context.
Cleartool.exe location & ClearCase Installation Type should be set automatically on a computer with a ClearCase installation, although they can be overridden manually if desired. ClearCase Installation Type enables and disables some options which are only available in ClearCase or ClearCase LT, respectively.