The interior of Shoes is unknown except for a display window that can be seen from outside which shows purses also available in the store. This goes for both episodes it appears in. It is most likely that they sell shoes and other footwear.
The exterior of Shoes looks like an average Bikini Bottom shop building. A display window is seen from outside. In "Whale of a Birthday" and "Mall Girl Pearl," it appears as one of the many stores in the Bikini Bottom Mall.