An output column is a column which is retained in its original form during normalisation. This contrasts to a normal column, which is mapped onto a key or category and then deleted.
You will use an output column to translate the results of an activation query back to a list of specific individuals. For example, the output column might contain a customer number or an email address.
You can use your bunker's web UI to mark a column as an output column.
Because output columns are only used in activation queries, they are only available in activation datasets. In an insight dataset, you won't see the option to mark a column as an output column.