ETL: That data over there is in that format, and that other data over in that other place is in that other format, and I want it all over here in this format.

ETL: That data over there is in that format, and that other data over in that other place is in that other format, and I want it all over here in this format. So I will extract it (get it out of those other places), transform it (put it in my format), and load it (store it here). The term has been around for decades and traditionally is used by database people, but it can apply to any process that does this. A concrete example might be if you run a business where you sell used books through Amazon and eBay. They each have their own format for info about the status of a product you have listed (whether it has sold, which shipping option the buyer chose, whether payment was received, etc.), but you might want to have that data from both sources in one place so you can see a dashboard or analyze it.