Hi Sayeem Chowdhury,
Thank you for reaching out to Microsoft Q & A forum.
The example uses a JSON parameters template to show how Azure Resource Manager (ARM) works with parameters, which applies to both Bicep and JSON. Even though you're learning Bicep, it's common to work with JSON for parameters, since Bicep compiles ARM templates in the background. Bicep can work with both Bicep and JSON parameter files, so this example is still useful. It's all about securely referencing secrets from Azure Key Vault, and this concept is the same whether you're using Bicep or JSON. Understanding this will help you work with both formats in real-world scenarios.
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