A fresh install refers to installing an operating system on a computer which does not currently have one. An in-place upgrade would be performed if you already had an operating system, and obtained the necessary compatible software to update it to a newer version. A fresh installation requires to manually download the correct version of Windows 10 that will upgrade your system. Technically, upgrading through Windows update should be the easiest and safest way to make the move to Windows 10. However, performing an upgrade can also be problematic.