Slash commands are application entry points that allow users to invoke Slack app functionality directly from the message composer. A user enters a forward slash followed by the registered command—for example, `/todo`—and Slack routes the resulting command payload to the associated application. The payload includes contextual information and any text entered after the command. The application must acknowledge the request promptly and can respond through mechanisms such as `respond()`, `say()`, or subsequent Web API operations. Slack's official documentation explicitly describes slash commands as allowing users to invoke an app by typing a string into the message composer. They are unrelated to message encryption, workspace theme configuration, or general channel deletion. Therefore, B accurately describes the purpose of Slack slash commands.