> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vessl.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Pipeline variables
**Pipeline variables** are working similarly to the environment variables in the pipeline execution. You can define the pipeline variables in the `Variables` tab and use them in the pipeline steps.
Navigate how to create pipeline variables with the demos below:
There are two types of pipeline variables:
* **Input Variables**: The variables that are injected into the pipeline steps.
* **Output Variables**: The variables that are generated from the pipeline steps.
## Input variables
Input variables are used within the pipeline and directly impact its output.
For **input variables**, you can define the following options:
* **Name**: Name of the variable.
* **Description**: Description of the variable.
* **Type**: Either `String` or `Choice`; For the `Choice` type, you can define the choice options. Both options are treated as a string, but the `Choice` type provides a dropdown menu in the pipeline execution.
* **Value**: Default value of the variable.
## Output variables
Output variables are a way to **pass the result of a pipeline** to another pipeline. For example, if you have a step that trains a model and you want to pass the model path to another step, you can define an output variable in the training step and use it in the next step.
For **output variables**, you can define the following options:
* **Name**: Name of the variable.
* **Description**: Description of the variable.
* **Source**: The source where the variable is generated. You can choose the either constant, pipeline step or input variable.
* **Value**: The value of the variable. If the source is a pipeline step, you can define the step reference and claim name.