A Resource Group is a group of resources such as virtual machines, databases etc. One resource group is associated with one azure subscription Azure resources hierarchy is as follows Management Group > Azure Subscription > Resource Group > Resources. It's important to note that one resource can be associated with only one resource group but a resource group can contain resources from multiple Azure regions. Resource groups are offered by azure at no cost we only pay for the resources and not for the resource gropup .To maintain the cost and billing of the different departments in your organization create different subscription. You cant merge two subscriptions into one however you can move a resource from one subscription to anoither.In case a subscription is expired you can't create a resource but data can be accessed . And Tags are used to identify applications, resources and environments for tracking and reporting purposes.

We deploy software or application on a cloud on a virtual machine. A Virtual machine with premium SSD or ultra Disk 99.9% SLA(SLA stands for service level agreement). A Virtual machine with a standard SSD will give 99.5% SLA. A Standard HDD Disk VM will give 95% SLA. Also, note that Availablity Set is a logical grouping of Virtual Machines Azure provides with two types of availability set that are 1 fault domain and 2 the Updated Domain. Fault Domain is the group of Virtual machines that share the common network connectivity and power supply while the Updated Domain is the logical group which gets restarted at the same time and all the maintenance happens in this group at the same time .So distributing VMs across multiple fault domains will increase availability. Scale set allows you to create and manage a group of Azure Virtual Machines.VM Scale set allows auto and manual scaling. There are two types of scaling vertical scaling and horizontal scaling vertical scaling increases the available hardware capacity while horizontal scaling it increases the number of virtual machines.