Business intelligence depends primarily on data. The best BI tools are able to pull data automatically or on-demand from a variety of sources. Others aggregate data in different formats, clean them structurally, and place them in a common data storage, ready for retrieval. Centralized solutions make use of data warehouses or data marts and extract, transform, and load (ETL) software, also know as integration services, to manage the data storage. BI tools are also able to analyze and uncover trends, present data in formatted reports and visual dashboards, compare performance using historical data against current data or internal data against competitor data, and use other analytical processes to describe situations more clearly.