On WindowsKeyGlobal.com, you will find yourself with multiple choice of licenses, according to your needs, your budget and your desired quality.

Here are the different types of licenses offered for each program:

Windows and Windows Server:

OEM License (Original Equipment Manufacturer): This is the key found on the original stickers (which are glued to the PC when sold), it remains valid for life on ONE computer (or server) even if formatted X times, you you can reuse it on the same computer. OEM is always 1 PC and not transferable. 
Volume License (or Retail): Single use, activates an X Number of PCs (After 30 days warranty before use) and it is lost when formatted.
Retail is like a balance, on the other hand OEM is a key valid for life on a single PC.

Office, Project, Visio and others:

Email License: This license attaches to your email address, it is saved online and becomes a service & subscription on your own Microsoft account.
Volume License (or Retail): Single use, allows to activate an X Number of PCs (After 30 days warranty before use) and it is lost when formatted or uninstalled.
Telephone activation: Activates the program by calling Microsoft. (It takes time to activate)
Online Activation: Activates directly online. (Instant activation)
 
Office 365:

Account: You will receive a pre-created subscriber Office 365 account for 2 years, you can change the password but not the email.
License: The license is free and can be attached to any Microsoft account.