In computing, an emulator is hardware or software that enables one computer system (called the host) to behave like another computer system (called the guest). An emulator typically enables the host system to run software or use peripheral devices designed for the guest system.
i.e. and e.g. are abbreviations of Latin phrases and each has its own specific meaning. i.e. stands for id est, meaning that is.. It is used to explain what exactly something means, or to say the same thing in other words. It is an abbreviation (Latin) of id est. Meaning that is.
Not sure what OS stands for? You hear it mentioned all the time, but you're just not 100 percent positive of what it means. That's okay, no problem. OS is short for Operating System. Windows is the most common operating system, but Linux and Mac OS X are also choices. Whatever flavor you enjoy, they all do pretty much the same thing. They give you a way to run programs and work with your computer.