If your home is indeed placed on the MLS ALL REALTORS who have a 'watch' on your community will be automatically notified via the MLS and/or email. REALTORS can view and send your homes data to the buyers who have compatible interest.
Your home will also appear in other professional websites if your MLS placement included IDX syndication. Unfortunately, if you choose that option, it also means you have lost ALL control of your homes data and it can appear anywhere for any purpose and for illegal purposes also. You will not be able to retrieve the data. Humpty Dumpty can not be put back together. But lots of folks will see it!
All that said, this does not mean your home will be shown. That is a whole different set of issues.
This is where analytics will prove essential for properly positing and adapting to market conditions.