Like the name suggests, Big Goombas are just larger versions of the regular Goomba. Mushroom-like bodies with brown shoes, big black eyebrows, and fangs on their lower jaw. Though they're not a complete clone visually; they're mouths will open and close and they'll have bigger steps.
Big Goombas act just like the normal Goomba, but this time, with a twist. Sure, they'll walk left and right like the Goomba, but now, when you stomp on them, they'll turn into two smaller versions of themselves. Big Goombas can appear in many sizes, and with each bigger size, the bigger the smaller version is.
Big Goombas act exactly like how they did in Newer Super Mario Bros. Wii. They'll walk left or right, and when you stomp on them, smaller versions of themselves will be created. Once again, they're able to be different sizes.