i donot know

the concept is tracing:-

mainly the tracing concept is coming in designer level. 

tracing means if u 2 tables, if u select one table column 
drag the cursor to the next table column. at that time 
cursor will turns into pencil symbol.

report tracing is nothing but tracing the report for its
performence by using audit we can trace report like
how many users seen it.and users details ,its perpormence etc.

tracing is nothing but keeping track of each and every 
operation performed on repor, who performed that and when 
performed. these operation includes, report opening, 
refresh, adding any object, delecting any object, change in 
query or even deleting report itself etc.. etc...