Screen scraping is the process of accessing data on a mainframe by having a program control the behavior of a terminal emulator. That is, the mainframe believes it is interacting with a human user operating a terminal, but the user is actually a program. The program sends data to the mainframe by typing on a virtual keyboard, and it reads the results from a virtual screen.
The x3270 family facilitates screen scraping in several ways. First, it has a scripting facility that allows an interactive session to run a program that automates some mainframe task. Second, there is a standalone variant called s3270 that is a pure screen-scraping tool.