These are the available editions of SQL Server, as told by the Editions Matrix:
After downloading/acquiring SQL Server, the installation gets executed with SQLSetup.exe, which is available as a GUI or a command-line program.
Installing via either of these will require you to specify a product key and run some initial configuration that includes enabling features, separate services and setting the initial parameters for each of them. Additional services and features can be enabled at any time by running the SQLSetup.exe program in either the command-line or the GUI version.