tail is a command line program for *nix like systems for viewing the tail end of files or pipes.
Tail is very useful for viewing log files, especially when you want to monitor the new logs being generated in real time.
tail [options] filename
Options that I commonly use:
View the last n lines of a file
tail -n filename
To monitor the tail end of a file (updates when new lines are added to the file)
tail -f filename
Continue to view a log file that get rotated
tail -F filename
To break out of tail, use
ctrl + c