A 2-shift (or two-shift) shift pattern is exactly what it sounds like: staff work one of two possible shift types, each covering a different block of hours.
For example, you might have one shift that runs from 07:00 until 13:00, and a second that runs from 13:00 until 21:00.
Typically, staff who work 2-shift patterns rotate, taking it in turns to work each shift pattern for a few weeks or a month at a time, as designated by their manager. During the normal course of their day, the staff who are finishing the first shift will usually “hand over” to the staff starting the second shift, getting them up to speed on the events of the day.