Basically, in some team-vs-team video games, teamwork matters much more than individual skill level. So no matter how skilled a player is, they can still lose consistently and be ranked lower than they "should" be. The skill rating system used is often the ELO system, and the "hell" here is a situation where a player is consistently matched with players far below their own skill level, due to poor teamwork.
There's also a lot more randomness in teamwork - sometimes a teammate has a bad day, or is just trolling. Successfully convincing the other people on the team to work as a team to accomplish objectives is often a counter-intuitive skill for people who focused on game mechanics and game knowledge.