The Repository Profiles contain all settings which are required to establish a connection respectively authenticate to a repository.
SmartSVN automatically creates a new profile, when opening a working copy, which contains a currently unknown repository URL. Typically, such profiles are not fully configured, because there are additional usernames, passwords or certificates required for a successful authentication. When commands are invoked, which are connecting to the repository, SmartSVN will query for this additional information.
Alternatively (and important for checkouts) the Repository Profiles can be configured from the Project Window and from the Repository Browser by Repository|Manage Profiles.