the ` is also known in programming as a backtick.

Usually, the backtick will be used in programming to execute a program and return the output.

Here are some useless examples:

bash (or other shells, not sure if they would work):
jason@dexedrine (~) (45) % cd /usr/src/linux/arch/`uname -m | sed s/i.86/i386/`/boot/
jason@dexedrine (/usr/src/linux/arch/i386/boot) (46) %


$listing = `ls -la`;
print $listing;

$listing = `ls -al`;
echo $listing;

I'm sure there are others, but these are the ones that are probably most commonly used.