The tier-and-division system, broadly speaking will separate players according to skill level and then, within that, note how close those players are to being promoted or demoted to a different tier, ranging from Bronze to Diamond.
The top tier, called Master, will display rank differently. Masters will have a badge showing how many rank points they have accumulated in that season's Master league. Grand Masters are Master league members who are the top 500 point earners in their region. Their badge will note that numerical rank. The rank is updated daily.
As a result of the new tiering system, only players within one league tier of one another will be able to queue together as a party in Hero League matches. Placement matches at the beginning of the season will determine where players go, and in those, only players playing their placement matches will be able to party up.
Additionally, players under a silence penalty for bad behavior will no longer be able to queue up in Hero League until that penalty experies.
Seasons will conclude with "epic rewards," Blizzard promised, which can double up if they're playing in both Team and Hero League. The post announcing the new changes revealed some pre-season loot Heroes of the Storm will be dropping top-ranked players before the season gets under way.