[nul_byte]

"The "Zen" of vi is that you're speaking a language. The initial y is a verb. The statement yy is a synonym for y_"

ok, so what is y underscore?

[sevensor]

This is maybe not the best example. I've used vi for a very long time, and I'm only now finding out about the underscore. The point that's being made here is that the first y is an action and the second is a motion. I was content to think of "yy" as a special case. Better examples would be yw, ye, yj, which respectively yank to the beginning of the next word, the end of the current word, and the current line plus the one following it.