> For the complete documentation index, see [llms.txt](https://gl-docs.gitbook.io/zkpass/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl-docs.gitbook.io/zkpass/zkpass-developers-guide/zkpass-modules/dvr/key-concepts.md).

# Key Concepts

Understanding the DVR and its functionalities revolves around comprehending three fundamental concepts that form the backbone of the system. These concepts are integral to the operations of DVR running on zkPass Service and are crucial for anyone looking to effectively utilize or develop with this application.

1. [**User Data**](/zkpass/zkpass-developers-guide/zkpass-modules/dvr/key-concepts/user-data.md)
2. [**DVR (Data Verification Request**](/zkpass/zkpass-developers-guide/zkpass-modules/dvr/key-concepts/dvr-info.md)
3. [**zkPass Proof**](/zkpass/zkpass-developers-guide/zkpass-modules/dvr/key-concepts/zkpass-proof.md)

The diagram below illustrates the relationship among the three:

<figure><img src="/files/IQz2S5Av2lqTVAZiWJEY" alt="" width="327"><figcaption></figcaption></figure>

At a fundamental level, the user data and the DVR Info, which contains the query, act as essential inputs to the DVR/zkPass. These two components are necessary for the generation of the zkPass proof.

## <mark style="color:blue;">Pipeline for Generating zkPass Proof</mark>

For a more comprehensive understanding of the zkPass proof creation, examining the query processing pipeline provides insight into how this process unfolds.

<figure><img src="/files/5CD1lZpBTA47cKzUMKdx" alt="" width="375"><figcaption></figcaption></figure>