SQL Server Installation - What is the Installation Media Folder?

For the SQL Server 2017 (Developer Edition) installation, I did the following:

1. Open SQL Server Installation Center
2. Click on Installation
3. Click on New SQL Server stand-alone installation or add features to an existing installation
4. Browse to C:\SQLServer2017Media\Developer_ENU and click OK

If you've downloaded SQL from the Microsoft site, rename the file to a zip file and then you can extract the files inside to a folder, then choose that one when you "Browse for SQL server Installation Media"

SQLEXPRADV_x64_ENU.exe > SQLEXPRADV_x64_ENU.zip

7zip will open it (standard Windows zip doesn't work though)

Extract to something like C:\SQLInstallMedia

You will get folders like 1033_enu_lp, resources, x64 and a bunch of files.