1.VMware vSphere is a software suite that includes components like ESXi, vCenter Server, vSphere Client, vCenter Orchestrator, vSphere Update Manager, etc. vSphere components provide virtualization, management, resource optimization and many other feaures useful for a virtual environment. vSphere is used to virtualize and aggregate the underlying physical hardware resources and to provide the pool of virtual resources to the datacenter. It also supports some advanced virtualization features such as disaster recovery, high availability, fault tolerance, dynamic resource allocation, etc.

Here is a list and description of the most important components included in the vSphere product suite:

• ESXi – a type 1 hypervisor. A hypervisor is a piece of software that creates and runs virtual machines. In vSphere, virtual machines are installed on ESXi servers.
• vCenter Server – a centralized management platform and framework that lets you manage virtual machines and ESXi hosts centrally.
• vSphere Update Manager – an add-on package for vCenter Server that helps you keep your ESXi hosts and VMs patched with the latest updates.
• vSphere Web Client – a web-based user interface used for managing a virtual infrastructure.
• vSphere Client – a locally installed Windows application with a graphical user interface (GUI) for all day-to-day management tasks and for the advanced configuration of a virtual infrastructure.

There are three vSphere editions:

• vSphere Standard
• vSphere Enterprise
• vSphere Enterprise Plus

2. vCenter Server

vCenter Server is the centralized management utility for VMware, and is used to manage virtual machines, multiple ESXi hosts, and all dependent components from a single centralized location.

vCenter Server can be installed on a supported version of Windows or you can use a preconfigured Linux version known as vCenter Server Appliance.

vCenter Server is required for some advanced vSphere features, such as vSphere High Availability, vSphere Fault Tolerance, vSphere Distributed Resource Scheduler (DRS), VMware vSphere vMotion, and VMware vSphere Storage vMotion.

A single vCenter Server instance can support a maximum of 1,000 hosts, 10,000 powered-on virtual machines

A vCenter Server instance consists of the following components:

• vSphere Client and vSphere Web Client – both tools can be used to manage your vCenter Server. vSphere Web Client is the recommended way to manage an ESXi host when the host is managed by vCenter Server.
• vCenter Server database – stores the inventory items, security roles, resource pools, performance data, and other information. Oracle and Microsoft SQL Server are supported databases for vCenter Server.