Metaprogression in roguelikes is the progress you make in between the individual runs. In some roguelikes, the metaprogression is sort of 'in the game' - you unlock upgrades or new items or something. A lot of people like that kind of thing! I prefer roguelikes where you get better by playing the game and improving your own skills/knowledge. In those types of games, the metaprogression is your own understanding and skill!