An event trace log (.etl) file, also known as a trace log, stores the trace messages generated during one or more trace sessions.
Because the messages can occupy a large amount of disk space, trace logs store them in a compressed binary format. To read the messages, trace consumers use information supplied by the trace provider (the FormatString parameter in the DoTraceMessage macro) to parse and format the messages so that they are readable. The trace consumer can find this information in the PDB symbol file or the trace message format file for the provider.
Build date: 2/13/2014