I don't know how new you are so forgive me if this is rediculously elementary but hopefully it clears some things up for you.. anyway:
First of all its important to differentiate galleries from free sites.. a 'gallery', that you will find at TGP's, is a one page wonder.. 12-30 pics usually with no other pages directly associated with it. A free site on the other hand, which is more relevant to this board as it consists more of link list owners rather than TGP owners, is a little miniature site with an enter/warning page, a main page which links to 2 or more gallery pages, and then the gallery pages - usually 2 galleries of 10 or more pictures or 1 or more videos ( most link lists have a 120 seconds of video OR 20 picture minimum requirement for free sites posted to them that they will link to ). These specifications if you will have kind have become the definition of a free site and a gallery only because of the rules set forth by the link list and tgp owners, respectively.
That said, the power is in your hands as a webmaster whether you want to be the poster or the postee, or any combination of the two. Sponsors provide galleries and ( to some extent ) free sites to webmasters which they host on their own servers and webmasters simply link to with their referral code. If you want, you can use only these freely provided 'hosted' galleries and/or free sites and not take any submissions. For variety though, not to mention reciprocal links, the goodness of their hearts (

- thanks guys!), and sometimes profit (much more so in the TGP world) you can opt to accept submissions from every Joe Schmoe in the industry.
This is just kind of a primer.. by no means does it contain enough information to really get you started, but hopefully you'll understand a bit more when you read stuff in the future.
QuickDraw