Using a pair of back quotes (`) will cause a shell to execute the back-quoted text as a command and substitute the output back into the original command.

Using a pair of back quotes (`) in shell scripting is known as command substitution. When you enclose a command within back quotes, the shell executes that command and substitutes the output of the command back into the original command. Note that the use of backticks for command substitution is an older method, and modern shell scripting encourages using the $() syntax for command substitution, which provides better readability and nesting capabilities.