Piano roll
The MIDI editor's grid: time runs to the right, pitch runs up, and each note is a rectangle whose length is its duration.
The name comes from player pianos, which from the 1890s were driven by paper rolls whose holes, by position and length, pressed the keys down. The digital version draws the same picture with a keyboard down the left edge. Below the notes there is usually a lane for velocity and CC curves, plus a quantize button that snaps everything to the nearest grid line.
Practically every DAW has one, and it has become the default way to write music without reading notation. Trackers went the other way, with vertical columns of hex codes, and still have their zealots.