Looking at your TPC page now shows Initiatives, which you can complete by doing everyday stuff like fishing and selling stuff at Retail. Check it every day and you'll earn MEOW coupons, which can be used to purchase stuff from a campsite that now appears to the east or west of your town map. The campsite is run by a dog named Harvey, who not only sells items himself that change each day, but hosts a camp for RVs to park in. Generally, each day there will be an RV with a random NPC, such as Jingle, Jack, Pascal, Saharah, or Gulliver. You can buy items from these RVs for MEOW coupons, too.
However, the update also added Amiibo capabilities, allowing you to use Amiibo or Amiibo cards to summon another Animal Crossing character to the campsite. In the case of NPCs like K.K. Slider, you can buy special items, like his guitar case. If you use the Amiibo cards to summon a VILLAGER, however, you can move them into your town. Favourite villager just moved out? Bypass the 16 villager cycle it'd normally take to get them back. Scan their card, invite them in, and you're golden. Already have ten villagers? It'll let you boot one out and they'll be in boxes that same day, letting your new villager move in as soon as possible.
In addition to MEOW coupons, there are more items from shops. Balloons now drop Welcome Amiibo items and other items, rather than just balloon items, as long as you've collected all the balloon furniture at least once. Fortune cookies now hold new items, like Nintendogs-related ornaments and special New 3DS and Wii U consoles, that allow you to play mini-games called Puzzle League (3DS) and Desert Island Escape (Wii U). And if you're having bad luck getting these from cookies, most NPCs you can scan into the campsite with Amiibo will sell a Wii U, and many sell personalized faceplate versions of a 3DS, again, like K.K. Slider.
Lastly, still regarding Amiibo, you'll find a genie's lamp on the ground containing Wisp. Wisp will adopt the image of a scanned Amiibo once a day, and call them to the campsite. He will give you 5 MEOW coupons a day for calling him out of his lamp. But, this is also how you get characters like Kicks and K.K. Slider in your campsite, but his abilities also aren't limited to Animal Crossing Amiibo. Scan certain Splatoon characters, or Legend of Zelda characters, and get special villagers like Epona or Ganon. Also with the introduction of these new Nintendo characters, there is a special set of Amiibo cards featuring Sanrio characters, letting you invite in Hello Kitty inspired villagers.
Plus, Welcome Amiibo introduces cards that let you invite in villagers that haven't been seen in ACNL before, like Vivian the Wolf, Boots the Alligator, and Sylvana the Squirrel.
Tl;dr: Most new capabilities are Amiibo related, but the ability to earn and spend MEOW coupons at the campsite and the addition of many new items, plus the two mini-games, are pretty cool too.