The graph below shows the difference between these terms.
Fragile systems will deteriorate from the moment they exist. They are vulnerable.
Robust systems persist for a long time, but once they encounter an unexpected event, they will break.
Resilient systems are able to recover from shocks but will never get better than they were.
Antifragile systems gain from disorder. They break a little all the time and evolve as a result, becoming less prone to catastrophic failure.
The logo of Antifragility.works refers to Hydra, the multi headed monster in Greek and Roman mythology. When Hercules attacked the monster by chopping of one of its heads, he discovered that it was immediately replaced by two new heads. With every attack it became stronger. Hydra was antifragile avant la lettre.