No matter how you sort the information in the processes list, any single process can be selected for further inspection. Simply double-clicking on a process in the list brings up a panel of detailed information about it. Let's take a look at one of those panels now.
The upper section of the panel gives you a summary of essentials: the parent process (that which initiated the one you're looking at now), the user, the process group, the percentage CPU use, and the number of recent hangs. The title bar of the panel tells you the process name and in parentheses, the corresponding process ID number.
The lower half of the info panel is divided into tabs. The first, Memory, goes into more detail about the process' memory usage. Alongside Real and Virtual Memory figures, it offers Shared, Private and Virtual Private. If that's not enough types of memory for you, just wait for the System Memory tab. We'll come to that later.
The second tab, Statistics, goes into much more detail. It tells you everything a hardened geek might ever wish to know about the way this process has been behaving since it was activated.
There may also be a third tab, Open Files and Ports, which displays a list of the files on the computer that this process is making use of. Note that these are files the process is using, not files that you have opened using the application. If you have a document open in Pages, that document's name will not appear in this list. At the end of the list, you'll see IP addresses or domains that the process is using, assuming its function requires some sort of network connectivity.
To be honest, most of the information in these info panels is more than most users will ever need, or need to understand. Experienced users are the only ones likely to ever have a need to check this kind of detail, and they know what all the jargon means already.
Now take a look at the lower section of the Activity Monitor window, the area with five tabs:
Let's go through those tabs one by one, to get an overview of what each one is about.
The CPU tab shows you a simple graph of what the processor in your computer is doing. By default, the bar graph shows what percentage of resources it is devoting to System-level processes (essential operating system stuff, shown in red) and what percentage is allocated to User processes (the apps you're trying to Get Stuff Done in). You're also given totals for the number of threads and processes the chip is coping with. Simpler versions of this graph can be displayed on screen all the time, if you're keen on knowing what's going on all the time; we'll cover that in the final section.
The System Memory tab is another graph, this time as a pie chart. It tells you how much of your computer's real memory is actually being used. The VM Size figure is the amount of hard disk space being used for virtual memory or swap file; Page In/Outs refers to chunks of data being swapped in and out of the virtual memory store by the operating system.