Yes @Donna, you can execute a module through playbook. You can do something like this:
ansible webservers -m service -a "name=httpd state=started"
ansible webservers -m command -a "/sbin/reboot -t now"
Each module supports taking arguments. Nearly all modules take key=value arguments, space delimited. Some modules take no arguments, and the command/shell modules simply take the string of the command you want to run