What does 'substrate scalable cluster ' mean?

Link: https://github.com/w3f/Web3-collaboration/blob/master/grants/grants.md
screenshoot:

What does ‘substrate scalable cluster’ mean?
I think that a substrate-node is not only one process in the future, is it ?

You can read more in the following issue of our collab repo:

There are already 2 teams working on this. One is funded via a grant, the other is being funded privately.