Lots of times people will ask open source projects how they can help if they aren't a coder. Generally every person can review documentation, help with translations to other languages, maybe donate some money, help with bug triage, and of course do person-to-person evangelism.
Feedback loops are the system where feedback about an item is given back to the originator of that item. So, at a restaurant the feedback loop might be from the chef's meal, to your table, to your comment to the waiter, back to the chef. That is fairly tight and it helps the restaurant become better.
In fast food restaurants the feedback loop is long - the chef prepares the food, you get it at the drive through, you eat it, and then maybe a week later you mention to the drive through attendant what you think about the food. She has no idea who your chef was last time and can't do anything about it. This is a "large" feedback loop and is not constructive.
Generally speaking, it's better to have a tight feedback loop
Helping Drupal by closing a feedback loops
In the case of Drupal, a quick change in your module configuration helps the Drupal developers know the most popular modules and themes. Knowing the most popular modules and themes in turn lets developers know where to spend more of their time in debugging, adding features, and improving code. The system works by sending a message back to the drupal.org server letting the server know which modules and themes are enabled, a little bit about the number of users and visitors your site has, and your email address/site slogan/mission. This information is only used in aggregate to help guide resources. Currently, the subject of which modules are used is hard to guess - modules are frequently downloaded, tested out, and discarded so download numbers are unrelaible. This system is a vast improvement on the "download frequency" test.
In a patch to the welcome message, Khalid Baheyeldin of 2bits Drupal consulting has provided these instructions on the welcome page to urge users to enable this feature. It's possible that in future versions it will be enabled by default.