You're seeing just the function join, go back to Slack.Web.Channels module for more information.
Link to this function

join(name, optional_params \\ %{})

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Joins a channel, creating it if needed.

Required Params

  • name - Name of channel to join

Errors the API can return:

  • channel_not_found - Value passed for channel was invalid.
  • is_archived - Channel has been archived.
  • name_taken - A channel cannot be created with the given name.
  • no_channel - Value passed for name was empty.
  • restricted_action - A team preference prevents the authenticated user from creating channels.