Cant figure out how to install vcenter, or even what OS it requires, help!

Question

Unfortunately, the excellent vsphere windows client has now been discontinued (or at least we assume it has because we get error message "you have restricted editing capabilities on a virtual machine of version 9...).  So now we have to figure out how to get the web client. 
We don't want to install vcenter, due to the unnecessary complexity and cost, but it looks like we have to.
Unfortunately, I cant find out how to install vcentre - I found a page with the prerequisites, but It didn't mention the most important piece of information - what OS it needs, nor how to actually install it from the iso.
We are using vmware essentials kit on a single host. We dont have any windows server licenses, so if vcenter requires this, vmware is out, unfortunately.
what OS is required for vcenter
is vcenter free?
Do we need vcenter or vcenter server, or are they the same?
how do we get it?
How do we install it?
How do we access the web panel?
Where is the documentation?  We have spent some considerable time looking for it.  The nearest is this page:VMware vSphere Documentation which is for vsphere, not vcenter, and only includes info about the vcenter appliance.  On this page is a documentation link to the right, but vcenter is not included in the list of products - its like it doesn't exist.
Why do vmware make it so hard to use vsphere now?  Why doesn't sphere simply come with vcenter, as it cant work without it now, or at least offer it as an option when installing vsphere.  It must be a show stopper for many people like us who want to evaluate vmware to virtualise a hand full of non HA environments,  but get stuck at this point.

Answer 1

Just to clarify, vSphere is a suite of products that includes vCenter, ESXi (The hypervisor) and a whole range of other products.
There is a free version of the ESXi hypervisor but it is limited in features and you get basic management options, no vCenter server to manage multiple hosts so you can't use HA, vMotion, DRS etc etc
The reason for the lengthy installation documentation is that customers have a wide range of requirements, however most will probably opt for the "simple install" option!
Documentation wise, I prefer the HTML version which you can easily search / browse: vSphere 6.0 Documentation Center
1) vCenter requires Windows Server, however you can also use the Linux appliance, saving a windows license. This is much improved in recent years however is still missing some functionality such as Update Manager that some customers will use.
2) No, you need a license for vCenter, it manages your ESXi hosts and manages your virtual environment. See: Compare VMware vSphere Editions and Kits Comparison | United States
3) vCenter / vCenter server are the same thing
4) You need to purchase it, or use a free 60 day evaluation
5) As per the documentation above. The simple install is your best option to get it instaled in 30 minutes, or try the appliance version (Import it onto a host, boot and follow the instructions, database is included, very easy to deploy and no additional licensing costs)
6) Via https://vCenter-Hostname:9443
7) As above