The HTTP updates involve publishing the content of the repository in a Web server. In this case, Microsoft Internet Information Server.
The aim of using this type of server is to increase the capacity of the system to deploy updates of the Virus Signature File and the product engine to network computers. By doing this, more computers will obtain the updates. If updates are deployed via TCP/IP, they can be deployed to up to 3,000 computers per hour. If updates are deployed through a Web server via HTTP, up to 25,000 computers can be updated per hour.
Read more information about Microsoft Internet Information Services.