The Campsite is the your home in Animal Crossing: Pocket Camp.
You can customize it with furniture, invite animals to visit it, share it with your friends and decorate it with useful items.
Be aware that the initial choice of Campsite theme doesn't influence your gameplay, it's purely cosmetic. However, items placed in the Campsite do influence your overall gameplay.
Pay attention to the Type of items you place and the Animals you tend to invite.