The anonymous HTTP API is a mechanism that allows you to create a web server whose content is generated by workflows. Examples of the kind of things you might use this for are:
•Show a web-form to users and store data they enter into the database
•Respond to a card reader that notifies Calpendo whenever a card has been swiped so that you can enable or disable an instrument or open a door.
•Have a workflow send out emails that includes hyperlinks for a user to click on, so the user can then enter or view additional information.
•Perform pretty much any kind of operation you want.
For more details, see the workflows description of the Anonymous HTTP Workflow Event.