《问》What's the difference of Environment variable and Shell variable?

《问》

What's the difference of Environment variable and Shell variable?

• An environment variable is a globally available, in a program and it child programs. A shell variable is only available in the current shell.
• Environment variables are NOT ONLY global/system-wide. Shell variables are private to the currently running shell, and they are NOT exported (passed on) to any child processes. Environment variables are exported to any child processes.