What Bash is and is not

On reading the preceding definition, you may have noticed a few things you might have expected are missing. There is a lot of confusion out there about what Bash is and is not. Here are some common misconceptions:

• Bash is not (necessarily) part of Linux. They are separate pieces of software. GNU Bash existed for several years before the Linux kernel was created, and runs on other operating systems too.
• Bash is not the same thing as SSH. SSH is a service and network protocol for running commands on remote computers. bash can be one such command.
• Bash is also not your terminal or TTY. Your terminal is a device for sending information to, and receiving information from, a computer. Terminals used to be hardware devices with a monitor and keyboard. Nowadays, for most users, they are terminal emulators, or software devices. Bash is a program that runs using your terminal for its input and output.
• Similarly, Bash is not the same thing as PuTTY, iTerm, or xterm. These are terminal emulators, not shells. Your terminal emulator is a program that understands and interprets text-based programs. Bash is one such program.
• Bash is not the command line, in the strictest sense. Bash has an interactive mode, which is an example of a command line, but many other tools have command lines, and not just system shells. The bc calculator tool is an example of another tool with a command line.

Now that you know this, if someone ever asks you for a PuTTY account on your server, make sure to set them straight!