On a high level,
Skylanders: SuperChargers is just like all of the previous games. While
Trap Team let you capture and supposedly turn Kaos good, it seems he has reverted back to his old ways, and this time he has created a massive weapon that is powered by The Darkness itself and is devouring all of Skylands.
With the use of special vehicles equipped with Rift Engines, you are able to get your skylanders through the portal network that Kaos has taken over and start freeing his captives and looking for a way to stop The Darkness before it is too late.
As you work your way through each of the game's levels, you will be posed with a side quest of each vehicle type (Land, Sea, Air), and while the only one you need in order to get through the level (and game) is a Land vehicle (included with the starter pack), the other two missions not only add a good bit of play time, but you will get star points that go towards your overall Portal Master Level, a feature that isn't entirely new, but comes with frequent enough incentives to keep you wanting to get to the next rank as fast as possible.
These vehicle missions essentially replace the element gates of past games. In those, you needed characters of the right element type in order to see all of the areas that the game has to offer. While all games before Trap Team let anyone with the right element open the gate (a plus for those of us that had older characters), last year's release made it so that only Trap Team members could open the gates. This made players that wanted to explore everything have to wait for Activision to release a Trap Team figure of each element (and some seemed to be held back to later waves in order to help drum up anticipation). While the new side areas are only unlockable if you have the right vehicle type, since one of each vehicle type has been easily purchasable since day one, the game might have found a nice balance between the two previous formats.
That being said, there is now little to no reason to actually change which character you are playing. Sure, there are still elemental boosts so that certain character types are stronger in certain zones, but the need to go through different styled gates was a big reason to have the player swap figures. Now, you just have to change the vehicle, and the figure you are playing with doesn't even have to be a SuperCharger. That being said, both the character and vehicle get a great stat boost if you pair them up correctly.
The addition of the vehicles also adds a new level of customization to your in-game toys. Each vehicle has a variety of features you can unlock and equip. For instance, Land vehicles have different types of engines, horns, wheels and whatever specialty item makes them stand out from the others. While most of these are unlocked by finding tool boxes in the levels, some are only unlocked the first time you put both the vehicle and its character on the portal at the same time.
These mods aren't just for looks either. They can change everything from how the vehicle handles, to its speed, acceleration and armor. You can also spend Gearbits, a new form of in-game money, to upgrade a vehicle's weapons or shields. Like the money collected by a character, Gearbits are stored on the vehicle that picked them up.
While Skylanders: SuperChargers's Story Mode is a major part of the game, the racing capabilities are just as important. As soon as you make your way back to Skylander Academy, an airship appears to present you with races for the different types of vehicles. Only two courses of each vehicle type are unlocked at the start (the others are released by buying Trophy Packs), and without the additional real-world purchases, you can only perform Single Races or Time Trials on the unlocked tracks. When you do use a Trophy, you then unlock Boss Pursuit, Supervillain Cup and Mirror Cup race types, as well as the two other courses for the type of Trophy you used.
In Boss Pursuit, you must chase down a specific enemy in their signature vehicle and attack them until they are defeated before they finish the race. When you do take them out, you put the Trophy back on the portal and then can use that Trophy to play as them in other races. After collecting bosses, you can then participate in the Supervillain Cup, where you take part in several races back-to-back, and from there is the same tournament race, but this time with the Mirror option turned on for each course - this of course has you having to rethink the paths and turns you've learned since everything is backwards.
SuperChargers is also the first Skylanders game to allow online co-op and multiplayer. With an Xbox Live account, you can either race against people online, or drop into a friend's game and help them out. While the online connectivity is something that fans of the game have been asking for since the beginning, the overall feel of the game doesn't change all that much with this feature added.