Attachments are turned on for all members. If you had previous attachments on the old vbulletin site, you can check by going to your settings and click on "Manage Attachments"
Attachments are useful for uploading some quick pictures or files into a topic. Everyone has about 10 mb of storage and that is separate from your gallery storage space which is currently 10mb for regular members and 20mb for AC Elite. I will be increasing this amount in the near future.
Also, searching has been turned on for guests with a flood control, this will make it easier to look through all topics organized by tabs when you are not logged in because that is controlled through the search feature.