Azure is a cloud services platform provided by Microsoft. Azure consists of more than 200 services, that includes Infrastructure as a Service (IaaS) services, Platform as a Service (PaaS) services, and Software as a Service (SaaS) services.
The 200 plus services includes services for various categories - compute, storage, databases, security, networking, content delivery, data warehousing, integration technologies, data lakes, analytics, blockchain, machine learning, artificial intelligence, etc.
Azure uses an elastic model, i.e. you can scale up or scale down the usage of the services as needed, and offers a pay-as-you-go approach for pricing.
Azure Region
Azure Region is a geographical region where clusters of Azure data centers are located, and are connected through a dedicated low-latency network.
Availability Zones
Azure Regions contain multiple isolated locations called Availability Zones, each of which contains an isolated data center having independent power, cooling, and network.
Org or Organization in Azure cloud represents the business entity or company that is using Azure cloud services.
All other entities on Azure cloud such as subscriptions, management groups, resource groups etc - hierarchically fall under the Org or Organization.
Azure subscriptions are logical grouping of services used by an organization, for which Microsoft charges the organization based on either a per-user based license fee or on cloud-based resource consumption.
An organization can have multiple subscriptions.
If an organization has many subscriptions, it can manage these subscriptions more efficiently by grouping them under management groups.
You can apply governance rules such as access, policies, compliance etc. on the management groups. All subscriptions within a management group automatically inherits these conditions applied on the management group.
Azure resource groups are logical containers that contain Azure resources and services related to a specific azure solution.
Generally, resource groups must contain resources that share the same life-cycle so that they can be easily deployed, updated and deleted as a group.