In Unix/Unix-like systems, prefix is the install location. A common value for prefix is: /usr/local
--prefix:
This is the option's flag to tell the program/script that someone is passing an argument and that argument is meant to be understood as the prefix value.
PREFIX
This is just a placeholder value. If you saw --prefix=PREFIX in help outputs of any scripts, it just means that you need to replace PREFIX with your preferred prefix value.
Thanks for that. So you mean PREFIX can be any install location say a random directory? If I don't fill this out will the installation take place in the current directory?