Form data is information provided by the user through interaction with an element in a HTML form (such as a text input box, button, or check box). The information is transmitted as a series of name and value pairs. CICS® can scan an HTTP request to pick out the form fields, so an application can obtain the data using CICS commands, without needing to receive and analyze the entire body of the request.
HTML forms explains more about forms and form fields.
An application can receive the value of a specified form field, or browse through the names and values of all the form fields contained in a request. You can specify code page conversion options if you need to convert the data into a different code page for use by your application.
The Web client sends form data in a query string when the GET method is used, and in the message body when the POST method is used. CICS can extract the data from either of these locations, so you do not need to specify which method was used. As an alternative, if the form data is sent in the query string, you can retrieve the entire query string using the WEB EXTRACT command. Examining the request line for an HTTP request tells you how to do that.
CICS only reads form data when CICS is the HTTP server. The facility is not available when CICS is an HTTP client.