The Distributions module is not included with the standard installation of TitleLeaf. It is an added service. It manages the process of sending data to third parties. Most often the third party is a wholesaler/distributor but it can also be anyone with an email address (such as a sales representative) or an FTP site (such as an epub conversion house). In its most basic sense, the distribution module of TitleLeaf allows a publisher to track what assets go where.
Before a publisher can begin sending assets to third-parties, distribution channels must be setup by the TitleLeaf support team. These channels are technical definitions of the arrangements the publisher has with the third-parties.
Note: TitleLeaf's distribution module connects to third party FTP/SFTP accounts, Dropbox accounts, Webdav accounts, etc. It is, in essence, an enhanced FTP application. Similar to an FTP application, it is the user's (aka, publisher's) responsibility to maintain the FTP account credentials by communicating with the third party (aka, the wholesalers/distributors).