# Extract Transform Load

ETL (Extract, Transform, Load) takes data from a source, reshapes it in a series of small steps, and stores it at a destination.

Apprentice · General · Updated October 29, 2026

In data science, we often work with large data sets to move them from one database to another. This process is called ETL (Extract Transform Load).

We **Extract** data from the source, **Transform** the data to make it match the format we need, and **Load** it into our destination.

If the data format at the source exactly matches the data format at the destination, then no transformation needs to be performed.

![Extract and Load only](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/cb4520c5273a45dc8da2d37092305dca.png "Extract and Load only")

In reality, though, data at the source almost never matches the format that we need at the destination. So a data flow would look more like this.

![ETL with several transformations](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/09/500ee50315ac48fdad8b735f58c5f114.png "ETL with several transformations")

Notice that there is not just one single transformation. Instead each transformation performs a single task as the data flows through the stream, then passes the data onto the next step.

All ETL processes begin with a **source** (data at rest), move through one or more **transformations** in a stream (data in transit), and then store the result in a **destination** (data at rest).

## Key terms

- ETL

Source: https://www.ask-codey.com/lessons/what-is-a-stream-extract-transform-load