Edge 2017: What scientific term or concept ought to be more widely known?

Basic Category Theory free online, Tom Leinster released his book under CC BY-NC-SA 4.0.

Graph Isomorphism update, by László Babai. “With this announcement, I am retracting the quasipolynomial claim. On the other hand, I affirm that significant progress has been made.”

Farfalle, a new mode for building a pseudorandom function (PRF) from a b-bit cryptographic permutation.

NsJail, a light-weight process isolation tool, making use of Linux namespaces and seccomp-bpf.

qc is a C frontend for the awesome QBE SSA backend written by Quentin Carbonneaux, written in Myrddin.

void, a terminal-based personal organizer outliner thingy.

The moving sofa problem, with nice animations.