Wirecast ships bundled with the freely available Darwin Streaming Server from Apple.
Be aware that when you use the built in Streaming Server it is running on your local machine and will use your local machines resources, thus slowing down Wirecast.
In addition each of your users will connect directly to your machine. If you don't have a lot of bandwidth (say you are on a DSL and your viewers are on the internet), you will not be able to host many viewers. One or two over DSL. Perhaps up to five or ten on a local network.
If you plan to have many viewers, you will want to use a hosted QuickTime Streaming Server.
File Location
The Streaming Server uses a file on the server to contain the specific settings for the stream. You need to define the name of that file here. When you send your viewers the URL to use, this file name will be a part of that URL. for example, if the File Location is "my_stream" and the Host Name is "www.stream.com" then your viewers will need to use this URL: "rtsp://www.stream.com/my_stream.sdp". This information is shown in the bottom of the window as you configure the settings.
Actions
When you have "Built-in Streaming Server" selected, the gear icon will have these three actions:
Open in QuickTime Player
The stream is opened in QuickTime Player.
This is a handy shortcut for you and saves you from typing "rtsp://..." into QuickTime Player.
Save Movie
A QuickTime movie is saved to disk which contains a reference to the configured stream.
This Movie file is very small and only tells QuickTime where to find your actual stream. It does not contain the data of your movie. When you are not streaming, this movie will not work for your users.
You can send this movie to your users or post on your website so that your users can view your stream when you are broadcasting.
Save Multi-stream Reference Movie
A QuickTime movie is saved to disk which contains a reference to all of your QuickTime Streaming Server streams.
You can send this movie to your users or post on your website so that your users can view your streams. QuickTime will then choose which stream to use based upon the users settings. This is a very handy way to broadcast multiple bit-rates at the same time.