Acute accent in programming

` Acute accent
'
"

[root@localhost ~]# echo `date`
Thu Feb 10 07:29:41 EST 2011
[root@localhost ~]# echo "date"
date
[root@localhost ~]# echo 'date'
date
[root@localhost ~]# echo "$date"

[root@localhost ~]# echo '$date'
$date
[root@localhost ~]# echo date
date