What is Microsoft Azure? Core services and concepts

TL;DR

• Azure is Microsoft's cloud computing platform, one of the three largest providers alongside AWS and GCP.
• Resource organization: every Azure resource lives in a resource group, which lives in a subscription, which lives in an Azure AD (Entra ID) tenant. Resources are deployed to specific regions, optionally spread across availability zones for resilience.
• Core compute: Virtual Machines (VMs) for IaaS, App Service for managed web apps, Azure Kubernetes Service (AKS) for containers, and Azure Functions for serverless.
• Core storage: Blob Storage for unstructured data/objects, Azure Files for managed file shares, and Managed Disks for VM storage.
• Core databases: Azure SQL Database (managed SQL Server) and Cosmos DB (multi-model NoSQL, globally distributed).
• Identity: Microsoft Entra ID (formerly Azure Active Directory) handles authentication and access control across Azure and Microsoft 365.
• Management: deployments are typically managed as code via ARM templates, Bicep, or Terraform, rather than clicked through the Azure Portal.

Azure is Microsoft's cloud computing platform, offering infrastructure, platform, and software services delivered from Microsoft-managed data centers. Alongside AWS and Google Cloud, it's one of the three providers that dominate the public cloud market, and it has particularly deep ties to organizations already running on Windows Server, Active Directory, and Microsoft 365.

How Azure organizes resources

Before looking at individual services, it helps to understand how Azure structures everything you deploy. This hierarchy is one of the first things that differs from AWS and GCP's account-based models.

• Tenant: the top-level Microsoft Entra ID directory that represents an organization. A tenant can contain multiple subscriptions.
• Management group: an optional grouping layer between the tenant and subscriptions, nestable up to six levels deep, used to apply RBAC and policy across many subscriptions at once instead of one at a time.
• Subscription: the billing and access-management boundary. Resource usage is metered and billed per subscription, and subscriptions are also where many service quotas apply.
• Resource group: a logical container for resources that share a lifecycle, such as everything belonging to one application. Resource groups make it straightforward to manage, monitor, and delete a whole set of related resources together.
• Region: a geographic location containing one or more data centers, such as West Europe or East US. Most resources are deployed to a specific region.
• Availability zone: within some regions, physically separate groups of data centers with independent power and networking. Spreading a workload across availability zones protects against a single data-center failure.

A typical resource's full identity looks like: tenant → subscription → resource group → resource, deployed into a chosen region.

Core compute services

• Virtual Machines (VMs): infrastructure-as-a-service compute. You choose an OS image and a VM size (a combination of vCPU, memory, and sometimes GPU), and Azure handles the underlying hardware and virtualization.
• App Service: a managed platform for hosting web apps and APIs without managing the underlying servers. It supports multiple languages and runtimes and handles scaling, patching, and load balancing.
• Azure Kubernetes Service (AKS): a managed Kubernetes offering. Azure runs and patches the control plane; you manage the worker nodes and workloads, similar to how Kubernetes works on any other infrastructure.
• Azure Functions: a serverless compute service that runs code in response to triggers (an HTTP request, a queue message, a timer) without provisioning any servers, billed by execution time and resource consumption.
• Azure Container Apps: a managed platform for running containers directly, without needing to operate a full Kubernetes cluster, aimed at simpler container workloads than AKS.

Core storage services

• Blob Storage: object storage for unstructured data such as images, backups, and logs, comparable to AWS S3. Data is organized into containers, with tiers (hot, cool, archive) for balancing access speed against cost.
• Azure Files: fully managed file shares accessible over the standard SMB and NFS protocols, useful when an application expects a traditional file system rather than an object store.
• Managed Disks: block storage volumes attached to VMs, available in different performance tiers (from standard HDD to premium SSD).

Core database services

• Azure SQL Database: a managed relational database compatible with Microsoft SQL Server, handling patching, backups, and scaling automatically.
• Azure Database for PostgreSQL / MySQL: managed versions of the popular open-source relational databases, for workloads that aren't tied to SQL Server.
• Cosmos DB: a globally distributed, multi-model NoSQL database supporting document, key-value, graph, and column-family data, with configurable consistency levels and automatic multi-region replication.

Identity and Access

Microsoft Entra ID (formerly Azure Active Directory) is Azure's identity provider. It handles authentication for Azure resources and is the same identity system behind Microsoft 365 and Windows Server Active Directory integration, which is a large part of why organizations already invested in the Microsoft ecosystem tend to default to Azure.

Access to specific resources is controlled through Role-Based Access Control (RBAC), which grants roles (built-in or custom) to users, groups, or applications at the subscription, resource group, or individual resource level.

Managing Azure as code

The Azure Portal is useful for exploration, but production environments are typically managed as code:

• ARM templates: Azure's native JSON-based Infrastructure as Code format.
• Bicep: a more readable domain-specific language that compiles down to ARM templates, now Microsoft's recommended default for native Azure IaC.
• Terraform: a cloud-agnostic alternative to ARM/Bicep, using the Azure provider to manage the same resources through the same HCL workflow used for AWS, GCP, or other providers.

Azure vs. AWS and GCP: rough service equivalents

Some categories map closely enough across the "big three" that having the AWS/GCP name to anchor against can make the Azure terms click faster:

Category	Azure	AWS	GCP
Virtual machines	Virtual Machines	EC2	Compute Engine
Managed Kubernetes	AKS	EKS	GKE
Serverless functions	Azure Functions	Lambda	Cloud Functions
Object storage	Blob Storage	S3	Cloud Storage
Managed relational DB	Azure SQL Database	RDS	Cloud SQL
Identity	Microsoft Entra ID	IAM	Cloud IAM

The underlying concepts are similar across all three; the main practical differences are in naming, default networking setup, and how deeply each platform integrates with its own ecosystem, Windows/Microsoft 365 for Azure, in particular.