Biology - Dichotomous keys
The information used to classify objects can be put into a key.  The
simple key below is a dichotomous  key. At each stage or branch in the
key a person has only alternatives to help them identify the objects.
For example, the group of six supermarket items was divided into two
groups based on whether they could be eaten or not. Each smaller group was
divided into two and so on until each item was in its own group.