what is the use of logwatch ?

Question

I want to know when "apt-add-repository" becomes mandatory to run in Ubuntu machine. Usually I used following two commands many times.
$sudo apt-get update
$sudo apt-get install

Answer 1

LogWatch is a customizable, pluggable log-monitoring system. It will go through your logs for a given period of time and make a report in the areas that you wish with the detail that you wish. Easy to use - works right out of the package on almost all systems.

for more details check this link:
http://linux.about.com/library/cmd/blcmdl8_logwatch.htm