In statistics and related subjects, “aggregation” refers to the summarising of related data into a higher level of abstraction.
For example, when calculating an average, multiple data points are aggregated and reduced to a single value.
When data are aggregated, they become easier to understand – rather than a multitude of values, there can be only one single one, which can then be more easily compared over a period of time or across different populations – but in the process, other information is lost, in particular the individual values of individual data points.
Data can be aggregated at different levels. For example, population averages can be available at the level of municipalities, counties, countries, states or continents.