Percentage of CPU time used by the current user.
Percentage of CPU time used by tasks that belong to the system (eg. processes owned by root, windowserver etc).
Percentage of CPU time used by tasks that are running using nice. These processes are using a non standard priority level to give them more or less priority.
Percentage of time that the CPU or CPUs were idle.
Some newer CPUs, like the Intel Xeon “Nehalem”, sport a technology called Hyper-Threading which allows two threads to run simultaneously on each core. Mac OS X presents this as 2 virtual cores per actual core, meaning a 4 core CPU will appear as 8 cores. So it’s normal for some Macs to appear to have twice as many cores in iStat and other system monitoring apps.
This is memory that applications or the system needs immediate access to, so it can’t be cached to disk. It will vary depending on what applications you’re using.
This is memory that is actively being used.
This memory is no longer being used and has been cached to disk. It’ll remain in RAM until another application needs the space.
This memory is not being used.
This is a comparison between your current battery capacity and capacity of it when it was new. For example, if your battery lasted 5 hours when it was new, a figure of 50% suggests you should get 2.5 hours out of your battery now.
The amount of battery “cycles” the battery has had. One cycle is defined as a complete discharge and charge of the battery, but partial discharge and charges also count. So, two half discharge and charges are the same as one complete discharge.
For some tips on how to get the most out of your laptop’s battery, please visit this Apple support page.