One of the most common use of Sed is text substitution that can be achieved with the s command.

In a terminal, type echo "Hello sed" | sed 's/sed/World/' and press Enter:

$ echo "Hello sed" | sed 's/sed/World/'
Hello World

"Hello World" should be output to the terminal.

The string "Hello, sed" is sent via pipe as input to the sed command that replace the word sed with World.

The syntax of a basic substitution command is s followed by the string or pattern to be searched and the substitution text. s command and strings are separated with a default / delimiter.