ABAP stands for Advanced Business Application Programming. The ABAP is a high level programming language that was created in Germany. Within the parameters of the ABAP user fields refer to fields in which the user can select data from a table to fill in the specified fields. We see user fields in everyday life on things such as job applications, credit card applications, review forms for products and many other things.
On the side of programming making user fields involves linking these tables to certain fields so that the user can choose how to fill in these fields based on their choices.