Bourne shell (sh) was the default Unix shell of unix version7. Most unix-like systems (Linux) continue to have /bin/sh — which is the bourne shell / symbolic link / hard link to a compatible shell—even when other shells are used by most users. It was developed by Stephen Bourne at AT&T Bell Laboratories, and it was a replacement for the Thompson shell, whose executable file had the same name—sh. It was released in 1977. It is basically used for shell scripting writings. This is actually Bourne Again Shell or bash. I am not going to redirect u to a any link, cause u can get easily on the net and get tons of answers.