About the Log Navigator
Choose View > Navigators > Log to view the logs Xcode generates during your development process. The log navigator lists the actions you have performed in a project or workspace.
There are two types of actions the log navigator lists:
Tasks. A task is made up of a set of discrete operations. A task log lists the operations Xcode performed to carry out the task. The transcript of a task log can be affixed to the entire task or divided among its operations. The types of tasks that generate task logs are building tasks, archiving tasks, and source control tasks.
Sessions. A session is a period during which an activity is performed. A session log is the transcript of the events that occurred during that session, such as the output of the debugger while you debug your application. Running or debugging an application generates a session log.

The log navigator contains the task and session list. When you select an item in this list, the corresponding log appears in the log viewer, in the editor area. You can filter this list with the filter bar. The filter bar contains the:
Recent filter: Shows the most recent task or session performed for its type. For example, when this filter is turned on, if you have performed several builds and debug sessions, but no archive or source control task, the log navigator lists only the last build task and the last debug session.
Filter field: Shows tasks and sessions that match the text you enter.
© 2012 Apple Inc. All Rights Reserved. (Last updated: 2012-01-09)