What is data warehousing?

Actions of the past have proven to be guidelines for the future...

Data Warehousing is a process by which any organization, or individual (yes individual) will have the ability to look at the "actions" performed in the past, present and have the ability to predict the near future. In my statement above when I say "action" it means different things. Action for a Financial Brokerage can be a trade, for a retail store can be a sale of merchandise, and for an individual it could mean dinning out or shopping for clothes.

For simplicity and understanding, I will write more from the perspective of an individual expenses and income.

As an individual one is filled with tens of actions on a daily basis. If we make a note of all those actions we are effectively building a data warehouse. I personally have a data warehouse of my own, that tells me where every dollar goes. 

One who Keeps track of ones income and expenses over a period of time is effectively creating a data warehouse for oneself.

This is what all the institutions that build data warehouses do. Keep track of every action via myriad of systems in a centralized location to perform analysis.