Windows OEM or disc?

[Gazeley]

I've decided that I will be getting Windows 10 for my new PC however I am confused about the methods of obtaining Windows 10. I've seen that Kinguin sells £20ish Windows 10 OEMs however I don't know how OEMs work and therefore I don't know how I'd install Windows 10 to my computer. Would I have to use a USB and another computer and download the OEM onto the USB and then onto the new computer? If not how would I get the OEM onto my new build? Or would it be better to dish out an extra £80 or more to get a disc Windows 10 and an optical drive which would make installing drivers for all other parts easier?

[Benjals]

These sites just sell the keys and some supply download links for the image files to install windows, best to just use the following though:
You download the Windows 10 image file respective to the key you purchased and make a bootable USB with it.
Microsoft supplies software to do this: https://www.microsoft.com/en-au/software-download/windows10 there are easy to follow instructions for making the USB on this page.
Once done, insert the USB into the target computer, select it as a boot option and it will load up and begin the installation process.
It will ask for the key during installation.

Oh and OEM is just the version of Windows supplied to manufacturers for installation on the machines they sell, I think it's discounted and that's why they are so cheap, not positive though.