Q:

App service plan pricing details

This is the details required to fill for App Service plan section

What should we enter for the number of instances while entering the details of the App service plan. How is the number of instances determined.
suppose a Web App Bot i depolyed in azure using a free account does not use any Virtual Machine..then does it mean the web apps do not need any Virtual Machines even when moved to production also.
When i check the Virtual Machines tab in the Azure portal https://portal.azure.com/  it says no virtual Machines to display.

A:

The Azure VM is where your web app run. So whatever plan you choose, there's at least one VM instance hosting your web app.

How is the number of instances determined.

The number of instance is determined by two factors.

Pricing tier of your App service plan. It decides the maximum of instance you can use. For Free or Shared pricing tier, web apps run on the same VM with apps belonged to other customers, you only need to input 1 if you want to calculate.
Your need. For pricing tier Basic+ (Basic, Standard, Premium), you possess more than one dedicated VM instance(You can check the explicit number in portal or here). Thus you can set the instance number from 1 to Maximum mentioned above, according to your requirement.

When i check the Virtual Machines tab in the Azure portal, it says no virtual Machines to display.

Virtual Machines tab shows the VM resource you create explicitly, while the VM hosting your web app is managed by Azure automatically. Thus you can't see them.

