What does "5 free Fed e-files" mean? Does it mean 5 different people can file with the same Turbo Tax code?

Sort of.  With the Desktop program you can prepare unlimited returns and efile 5 Federal returns (for different people) for free.  The rest you can print and mail.  Like to do your family's returns.  

re:  turbotax deluxe 2019

can the desktop sw be installed on 5 different pc's for 5 different fed e-files?

or do all 5 fed e-files have to be created on the same desktop?

Either.  You can install Turbo Tax on up to 5 computers.