When you install ShipInsure, it adds itself as a product to your store. When someone clicks on the widget, it adds the “product” (i.e., ShipInsure) to their cart. This is why it shows up as a product in your store—so that when people click on it, ShipInsure will add itself to their cart.
If you are seeing the ShipInsure product listing in sections of your store you don't want, like "Featured Products", "Top Sellers", etc. you can follow these steps to exclude ShipInsure from those lists.