Tracing involves a specialized use of logging to record information about a program’s execution. This information is typically used by programmers for debugging purposes, and additionally, depending on the type and detail of information contained in a trace log, by experienced system administrators or technical-support personnel and by software monitoring tools to diagnose common problems with software.
In short, tracing is the process of recording what an application did. Such information can be really useful afterward, especially for debugging and fixing issues.
With detailed tracing information, it should be possible to “go back in time”, reenacting the sequence of actions performed by the application.
You might be thinking that this sounds suspiciously like logging. You wouldn’t be the first to make that connection.