Running programs are normally ephemeral: their data in memory is lost when you turn off your computer or end the program's process, unless you go to the extra work of saving your program's data.
Eternal is a research project into creating a programming language which automatically saves your program's data to persistent storage so that you don't have to manually.
This is a high risk research project: I have some ideas for how to make this not horrifically slow, but they might not work out.
And it's a high reward research project: if it does work out, it may dramatically simplify this aspect of writing programs.