Hypercore is a single writer append-only log. The website has a bit more info about how it works, but's basically a merkle log signed by a private key / public key scheme. We build collaborative data structures by combining multiple Hypercores.

Hyperdrives builds a p2p filesystem on top of Hypercore for a single writer. Using mounts you can mount other peoples drives so merge conflicts don't happen since there is no overlapping writes.

We are working on a union mount approach as well for overlapping drives (we talk a bit about this in the post)