Dr. DivX may be good, but there's always room for improvements and there is a dedicated team working 'round the clock to make the doctor a more capable physician. By ticking the Check for Updates option, you will allow Dr. DivX to quietly and periodically ask the Dr. DivX website if a newer version of the doctor is available. If an improved doctor is waiting in the wings, Dr. DivX will prompt you to upgrade.
Dr. DivX will use the Internet to look for new versions of Dr. DivX, but only if the Check for Updates option has been selected.