A talk page is a parallel page attached to other pages. This permits people to discuss the content in blog form. In this wiki this is accessed by a link to discussion. This is unfortunate since the same word is not used consistently, by default mediawiki-based services use the prefix "talk:" for these pages not "discuss:". That may change, since you "discuss Main Page" not "talk Main Page" in proper English. Some talk pages:
One function of talk pages is to debate the next version of the concept or deliverable discussed. This wiki tries to separate the latest proposal, e.g. next Main Page is the current standing proposal to replace the Main Page with something radically different (if you only want to make a minor change, make it yourself, noting why on the talk page).