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Welcome to the first lesson in this Azure fundamentals series. Across three short lessons,

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we'll follow one simple example: a small web app where people upload photos. In this lesson,

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we'll look at where that app runs: an Azure virtual machine.

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Here's our example. A user opens the web app in their browser, and the request travels across the

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internet to Azure. The architecture you'll see is illustrative. Names, sizes and values are samples

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chosen to explain the ideas, not recommendations.

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The app needs a computer to run on. An Azure virtual machine, or VM, is a computer that you create

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and configure in Azure. It's virtual because it runs on physical servers in a Microsoft datacenter.

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Azure manages that physical hardware, and you choose what runs on the VM.

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When the user uploads a photo, the request travels from the browser, across the network,

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to the VM. The web app running on the VM handles it and sends a response back. Notice the two layers:

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the VM is the computer, and the web app is software we install and run on it.

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Keeping those layers apart really matters. Azure provides and runs the virtual machine,

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but the operating system and the app on it are yours to configure, update and secure.

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If the app has a bug, the VM can be perfectly healthy. The fix happens in your software,

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not in Azure.

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When you create a VM, you choose an image, which provides its operating system. Azure offers Windows

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Server and many Linux distributions, such as Ubuntu, which we use in this example.

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The operating system is installed on the VM's OS disk, which we'll look at in a moment.

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Next is the VM's size. The size determines the compute resources available to the VM,

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such as the number of virtual CPUs and the amount of memory, along with limits like how many data

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disks you can attach. Sizes are grouped by purpose: for example, general purpose,

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compute optimized and memory optimized.

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To communicate, a VM needs a network interface, or NIC. Every VM has at least one.

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The NIC connects the VM to a subnet inside a virtual network and gives it a private IP address.

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It can also have a public IP address, if you add one. Virtual networks are the topic of Lesson 2.

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Finally, disks. Every VM has one OS disk, which holds the operating system. You can attach data disks

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for applications and data. Most VM sizes also include a temporary disk for short-term data,

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like page or swap files. Its data might be lost during maintenance or when the VM is stopped,

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so never keep important files there.

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Let's recap. A VM is a configurable computer in Azure. Its image provides the operating system,

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its size sets the compute resources, its network interface connects it to a virtual network,

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and its disks store the operating system and data. Next, we'll zoom into that network.

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And the uploaded photos? They'll go to Blob Storage, in Lesson 3.