TraceViewer is an application that allows tracing of network elements and subscribers to monitor network quality and troubleshoot problems. It collects trace data from elements and stores it in a database where it can be viewed as reports. Key features of TraceViewer include activating new traces, stopping traces, deleting traces, and viewing trace reports. The architecture involves TraceViewer installing on Linux servers with a GUI accessed via Java WebStart, while background tracing processes activate traces in network elements and collect data.