This is what's called a Tetris "line race" (also known as a "sprint"), in this case an attempt to clear 40 lines in the minimum possible time. This is the kind of thing top-level Tetris players do when they're bored, and/or want to prove that they are truly the best in the world.Found at Mental Floss. Note that in this Tetris game the position of pieces can be adjusted after they have fallen.
The player here is a Japanese woman player* who goes by "Keroco," and he or she achieved 40 lines in 19.68 seconds. That's the first time that someone has broken the 20-second barrier, and it's astonishing, to say the least. (A few years back, 40 seconds was considered a great time.) Tetris champion Ben Mullen wrote of the feat, "Let me humbly submit that this may be the greatest achievement in the history of gaming. ... This won't make national news. But to be honest, it should."