In a dynasty league, rosters carry over from one season to the next. Instead of drafting a whole new team every year, you keep almost all of your players and only add new ones through rookie drafts, trades, and waiver wire pickups. This makes the league feel less like a yearly contest and more like being a general manager of a real franchise.
Because rosters stick around, dynasty owners think about both winning now and staying good later. A young player with a bright future can be worth more than an aging star, even if the star scores more points today. Trades often involve swapping draft picks years in advance, and some teams that are struggling will "rebuild" by trading veterans for young talent and picks.
Dynasty leagues come in a few flavors. Some are standard dynasty, where you keep everyone. Others are "hybrid" or "keeper" leagues, which sit between redraft and dynasty by letting each team protect only a handful of players. Startup drafts for brand-new dynasty leagues are especially exciting, because every pick balances a player's current value against how long he might stay productive.