Overtuned heroes, look to first pick or ban.
High impact, low variance hero choices.
Slightly more situational than tier A heroes, but can still be impactful with/against the right compositions.
Niche heroes, should typically only be picked in order to counter the enemy team or play to map/team-specific goals.
Heroes which almost always have a better counterpart. It's possible to win with these heroes, but its significantly harder.