Top is an interactive command line program and looks like:
For a long time I had been using ps - aux as a way of seeing just what processes were slowing down a server or *nix based computer. However top is a far better tool for this task as it shows a real time view of processes. There are very few commands available and they can be found by typing ? once the program has launched. The most useful for my purposes is o, after pressing o, type cpu, to have top order all processes by cpu usage to find any runaway processes.