it depends on your webhosting provider. Some providers offer a real cronjob. If you own a dedicated server you should be familiar with
crontab to create a cronjob for wordpress.
The CommentGrabber works with normal WordPress Cron. But I recommend it to not slow down your blog in any way. This is just a recommendation to prevent people blaming me for their slow blogs.
This said you have to test if you can live with this setting without a real cronjob.
If you want to disable the WP-Cron you have to put this line of code near the beginning of your wp-config file:
If you don't really know what this is all about then just leave the settings as they are and the CommentGrabber will work the normal way.