A channel refers to the medium by which an article is available. Salesforce Knowledgeoffers four channels where you can make articles available.Internal App: Salesforce users can access articles in the Articles tab depending on their role visibility.Customer: Customers can access articles if the Articles tab is available in a community or Customer Portal. Customer users inherit the role visibility of the manager on the account. In a community, the article is only available to users with Customer Community or Customer Community Plus licenses.Partner: Partners can access articles if the Articles tab is available in a community or partner portal. Partner users inherit the role visibility of the manager on the account. In a community, the article is only available to users with Partner Community licenses.Public Knowledge Base: Articles can be made available to anonymous users by creating a public knowledge base using the Sample Public Knowledge Base forSalesforce Knowledge app from the AppExchange. Creating a public knowledge base requires Sites and Visualforce.