The RESTful WebAPI uses newer standards than our older SOAP WebServices to allow for more options in how the functions can be implemented. Some functions are able to use a rep or customer context directly through the use of an OATH token rather than using an API USer Account through SimpleAuth.
OAuth Tokens are avalailable when authenticating reps and customer through either the Token function or through Single Sign-On (SSO) functions.
WebAPI can be accessed from https://webapi.bydesign.com/client for most clients or https://webapi.securefreedom.com/client for some older installs. As the Shopping Cart uses WebAPI for the browsing experience, it can be a create resource to use when understanding the call flow and getting specific function call examples. The calls made can be seen in the Network section of the Developer Tools in most modern browsers when accessing and using the shopping cart.