As the name suggests, the previous value calculation feature populates the previous values of one column into another column

When creating a previous value calculation select the previous value type, and the table and column to calculate in the first form section. This example will store the previous owner of a case. In this example new_previousowner is a polymorphic lookup to the user and team table as owner may be either of these types

In the next previous value section we only need to enter the column of which the previous value is being captured

This screenshot of audit history shows previous owner being captured by the example calculated field