When speaking of Linux, iStat refers to a server. It is an open source project and it can transmit data and statistics from one's computer to the iStat on iOS.
ISTAT stands for the International Society of Transport Aircraft Trading. They are the leading company in trading by aircraft and the company is very successful.
Free of copyright restrictions (generally speaking).
Just as Macintosh people use a widget called iStat Pro to find out detailed information about how the system is running so Linux people use TOP. If you need a copy of TOP then you can download it from SorceForge.
Technically speaking linux is a kernel. The kernel is the part of the operating system that acts as a middleman/translator between the hardware and the software.
Strictly speaking, it isn't a matter of what Linux can do and what others cannot; most of the software available for Linux was written for older ones or has been ported. What is special about Linux is its low cost and its high performance compared to other common alternatives.
Linux is a kernel. It does not provide any other features of an operating system (such as an interface or programs). Linux is roughly the equivalent of ntoskrnl.exe in Windows 2000/XP/Vista. Complete operating systems containing the Linux kernel are usually referred to as "Linux distros."
Generally speaking, yes. There are certain extensions to PHP one could install on Windows that would provide functions that aren't present on Linux.
Generally speaking, no. Windows has a slower patch cycle than most Linux distributions, thus exploits are exposed for longer and have a greater probability of being hit.
The accronym "GNU" stands for Gnu Is not Unix. Technically speaking, it's "GNU/Linux" because Linux is the kernel, not the whole thing, we just shorten it to Linux (I do this myself, but I do know that Linux is just the kernel). It is made up of the Linux kernel and several GNU programs (try typing a basic command into a terminal with --help, chances are you could easily find one that says GNU somewhere at the bottom).
Strictly speaking, a "shell" is simply the interface between the user and the rest of the operating system. In that definition not all shells on Linux are command lines. However, most day-to-day usage of the term "shell" does refer to command line user interfaces. Finally, "Linux shell" is not a thing. Linux is an operating system, specifically a kernel, not a shell. Most Linux distributions use BASH, but I personally prefer ZSH.
Linux strictly speaking is a kernel used in many different operating systems. The simple answer is "the linux kernel" but that's not entirely correct, depending on whether the question is about Linux the kernel, or the often misused label "linux" meant to refer to any one of several hundred operating systems that run over the linux kernel. In my opinion, the defining component, the dominant trait, of linux is the modular design of the kernel. It need only be as big and complex as required, making it very small and simple, or a monolithic giant that can do anything, or anywhere in between.
Generally speaking, Alt+F1. However some DEs do accept Windows/Super key as an alternative.