Toy Story 3: The Videogame is broken up into two main modes. There is the game's Story Mode where you help Ham, Rex and the rest of the gang tell the story of how they came to their new home to their new friends. The other mode is a small open-world, mission-based experience called Toy Box Mode where you play Woody and are working to keep order in the dusty town of Woody's Roundup and help to bring it to the glory it should be.
The story-progressing levels tended towards the action/platformer side of things as you will have to navigate various larger-than-life locations in order to reach some set of goals the game throws at you. These missions let you swap between the three main characters with the click of a button, and you will need to swap characters often in order to use each one's unique abilities. Woody's abilities include using his pull string in order to grapple onto various items, as well as his higher jump, while Jessie can land on smaller platforms, and with the push of a button, reach areas the other two can't. Finally, Buzz's biggest boon is his ability to throw the other two characters far, which means you will often have to switch to him, throw a character, and switch back to the toy you just threw in order to get through the levels.
The Toy Box drops you off in the little town and has you going around and getting missions by talking to the various citizens, most of which are a mix between three-eyed alien toys and Fisher Price people. You will also put a lot of work into customizing this town as you gain the ability to paint buildings, dig for gold and place new storefronts on various lots in the town. Pickups you get both in this mode and in the Story Mode help to improve the town as you gain the ability to buy characters, like Bullseye, or new ways to customize the various storefronts. You will also find costume pieces throughout the game that you can use to dress up the aliens and Fisher Price people (by picking them up and throwing them into the different stores).