Application Directory
This is the path on the target client that contains the assembly hosting the Update Controller.

•Update Package Directory
This is the path on the target client to the temporary folder.  Actions can place files here or read from files that other actions have placed.  It is a temporary working directory for the update process.

•Log
The reference to the Log object allows you to write output to the text log file.  This is primarily for diagnostic information.

•Shared Properties
The shared properties reference exposes a dictionary that allows you to place object references that can be consumed in other actions, or conversely, access objects that you have placed from other actions.

•State
The state reference allows you to get the current state of the update that is in progress.  Possible values include Prepare, Execute, Cleanup, RollbackExecute, RollbackPrepare.