tmux Tutorial - Split Terminal Windows Easily[web search]
Terminal and Terminator
It was long time ago when I realized that the major part of my work is being done in the Linux terminal. This is why I pay attention to things like shell and GNU tools, because knowing them well is often more than a half of job done.
Afterwards, I found out that having just one terminal window is not enough. Even though having many windows (represented by tabs in Linux terminal-handling tools or by many Putty instances) can solve this problem, it is often desired to keep things in sight at the same time. For example, we may want to execute some code or tests and at the same time watch over log files by using tail.
Terminator seemed to me the right tool to do the job. It's easy to install and it does exactly what it's supposed to do - it can split terminal windows both horizontally and vertically, according to user's requirements. It also allows to keep multiple tabs opened in case splitting one window is not enough. Its important disadvantage is that Terminator is a GUI tool, so it won't work if an X server is not at hand.
Terminator in action: