So what exactly is PBE Ninja Tabi going to work against?

It says it'll reduce damage from on hit effects, but what exactly does this include?

I ask this because Guinsoo's Rageblade says it'll apply on hit effects twice every other autoattack, but it doesn't apply sheen twice, or stuff like Jax's Empower; however, it does apply Bork and Nashors Twice

So will ninja tabi reduce damage from only the obvious on hit effects, such as bork, or will it also reduce damage from everything? I.e. Jax's W, Sheen,