ULS stands for Unified Logging Systems, and it is a SharePoint component that produces log files under the 14 folder. A very easy way to read it is to use some of the tools presented in my previous blog post SharePoint ULS viewers. Btw, at least and according to me, the best one is still the Microsoft ULS Viewer.
The good news is that custom code can write to the ULS too, so in this way it is possible to have a single point of tracing.
In the Microsoft article Trace Log Example you can find an example of a custom tracer.
And in the post Logging to ULS in SharePoint 2010 is it possible to find a custom LoggingService writing the name of the tracing application.