Commerce Cloud Documentation

Dustin Tran is correct that some of it is currently private. Commerce Cloud documentation is available in the Commerce Cloud XChange site and what is often called: Infocenter. The prior is somewhat analogous to Salesforce SE whereas the latter is more traditional API documentation and product manuals. Infocenter is publicly available as of January 2019.

In order to access XChange, you must have an Account Manager credential that is granted by a partner or customer organization that has a standing contract with Commerce Cloud.

Additionally, the support team has developed some Knowledge Base Articles that are accessible if a customer or partner organization has created a Support account for you. These articles are supplementary to the Infocenter documentation.

Commerce Cloud documentation is available to the public now: https://documentation.b2c.commercecloud.salesforce.com/DOC1/index.jsp