> For the complete documentation index, see [llms.txt](https://docs.rainbird.ai/rainbird/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rainbird.ai/rainbird/knowledge-modelling/modelling-features/concepts/concept-instances.md).
# Concept instances
## Overview
For any given concept a concept instance is its data. You can think of concept instances as examples of the concept. i.e. given a concept of `Country`, the instances could be `France` or `Germany`.
Only concepts with a `string` data type allow you to create your own instances.
Concepts with a data type of `number`, `date` or `true/false` do not require instances to be explicitly created.
Opening a concept with a string data type will display an instances section and you can add instances like this:
{% hint style="warning" %}
**Validation**
Concept instance names must:
* Be unique
* Be less than 2,000 characters
* Not contain the following characters `"` , `'` , `\` , `<` & `>`
{% endhint %}
## **Metadata**
Additional information about a concept instance can be added as metadata, if it is necessary to provide further context about it e.g. providing an explanation of a particular tax code.
This data can be presented to end-users, if required, when the instance is referenced in a question or a result from Rainbird.
The image below shows an example of Metadata added to a concept instance. This input can be expanded for large metadata:
The below image shows an example of how the Metadata could be presented with a result:
This data can also be formatted using markdown. More details can be found on supported markdown [here](/rainbird/knowledge-modelling/modelling-features/other-features/markdown.md).
---
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