From the D&D Adventurers League website:
D&D Encounters remains our weekly Wednesday play program, but undergoes a facelift starting with Tyranny of Dragons and the introduction of the D&D Adventurers League. While you'll still find D&D Encounters emphasizing play for the casual player (starting characters at 1st level) you'll find it's become an introduction to the main storyline.
We'll introduce this storyline by adapting a portion (levels 1-4) of the first adventure, Hoard of the Dragon Queen, for play at D&D Encounters. This adventure adaptation will be available as a complimentary PDF for stores that schedule D&D Encounters, who can then pass it along to their Dungeon Masters. After you've finished playing that portion of the adventure, you can continue play by picking up the rest of the adventure from the store or play in D&D Expeditions.
The kits for D&D Encounters have been upgraded as well. Redesigned to immerse you in the story and the factions, each kit includes player (faction) and DM packs. These packs come in a beautiful folio designed with your faction's colors and symbol. When you arrive for your first session of D&D Encounters, you'll choose a faction pack with all sorts of goodies contained within – blank character sheets, log sheets, table tents, special certificates, and more. Dungeon Masters will receive a pack themed to the storyline, containing stuff for their use.