What are vSphere, vCenter and ESXi?

What do these terms mean?

When I became an IT professional, terms like vSphere, vCenter and ESXi used confused me, I always thought what do they mean in the “Virtual World” of VMware.

I am sure, I was not the only one and there are many more people who are still confused!

Hence, I am hopeful that this post will end this confusion and increase our understanding of Cloud Computing and VMware technology.


VMware is an American software company that creates virtualization software and provides cloud computing services.

ESXi and Workstation PRO are Hypervisors made by VMware. While vSphere and vCenter are managment tools created by VMware to administor ESXi hyperviors.


Hypervisor is a software that runs and manages Virtual Machines.

There are two types of hypervisors:

Type 1 Hypervisor:

  • This type of hypervisor is there purely for running VM’s, it does not need another OS to run its VM’s. It is installed and run on bare metal hardware— (a computer without an OS like Windows, Linux, Mac, etc). This type of hypervisor is a stand alone system that does not need another OS to help manage it’s VM’s.

Type 2 Hypervisors:

  • This type of hypervisor runs on a host operating system such as Windows, Mac or Linux etc. The host OS provides visualization services, such as I/O device support and memory management. A type 2 hypervisor “sits” on top of another OS and uses its resources to manage it’s VM’s.


This is a Type 1 hypervisor — its a software that is installed on bare metal hardware. It is this ESXi hypervisor that allows one to create and run multiple VM’s on a large server with huge amounts of resources


vSphere is a management interface that allows users access on a per server basis. vSphere is accessed via a web browser with the IP address of the ESXi host.

Diagram of ESXi Host and VM’s

The machine on the left has too many resources for one computer to use, hence if we install an ESXi on top of it, and create different VM’s, we can use these resources to their fullest.

These VM’s will use portions of the large server’s resources.

In order to access each host, you will type its IP into the web browser and access it from there. The drawback is that you can only access one host at a time with vSphere.


vCenter manages different ESXi hosts, their resources, networking, memory etc — all on one platform. It is a central management interface to manage all of your ESXi hosts and VM’s.

It comes with advanced features that allows many different actions such as VM cloning, vMotion, High Availability, Fault tolerance DRS etc. vCenter appliance normally sits on top of an ESXi host as a VM.

Once it is up and running — ESXi hosts are added in the inventory of the vCenter appliance. When this is done, vCenter automatically start picking up any VM’s in ESXi hosts and any changes that happen in these hosts.

Features of vCenter


vMotion allows movement of one VM from one ESXi host to another.

VM Cloning

VM Cloning tool creates an identical VM on the ESXi host.

High Availability

If a Virtual Machine malfunctions, another VM is created to take over the workload of the malfunctioned VM. High Availability minimizes interruptions to an operation.

Fault Tolerance

If a Virtual Machine malfunctions, other VM’s make sure that the work load does not stop while the malfunctioned VM is removed and swaped for a brand new VM. Fault Tolerance prevents any interruption to the operation.

DRS- Distributed Resource Scheduler

DRS spreads the virtual machine workloads across vSphere hosts inside a cluster and monitors available resources for you.

Workstation Pro

This is a type two hypervisor, you can install it on your personal computer, and create VM’s within the workstation pro application. Your local OS will provide services like memory management, disk space and processing power for the virtual machines.

So this is what vCenter, vSphere and ESXi mean. I am hopeful my explanations solved any confusions about these terms in your mind.

I am a student of IT, If you find any mistakes or misinformation, please contact me so I can learn and grow.

Systems Engineer | AWS Certified Cloud Solutions Architect