What is the purpose of the summary type 'sum' in search results?

The summary type 'sum' in search results serves the specific purpose of adding together all the values found within a specified column. This is particularly useful in analytical scenarios where you need to understand the total of numerical data, such as sales revenue or quantities sold over a defined period. By using 'sum', you can derive a clear total that reflects the cumulative value of the entries being analyzed, allowing for better insights into overall performance or trends.

In contrast, the other summary types involve different calculations unrelated to summation. For instance, calculating an average, minimum, or maximum would focus on different aspects of the data set rather than providing a total amount. Thus, choosing 'sum' as the summary type precisely targets the goal of aggregating the values, making it the correct choice for this question.