Filters are an extremely useful feature of the widget. A filter is a way of restricting the fish shown in the widget to a criteria that you specify. For example, you may want to only see Largemouth Bass that you have caught in the Live Well or on the Map. Or you may want to show only Channel Catfish that you have caught at a specific lake in the last 60 days. You can do all this and more.
There are two places to access the filter. You can access it directly from the widget by pressing the filter icon, or you can press the filter button while in the Live Well. The fish count displayed in the widget will change based on the number of fishing matching the filter. Are you in a tournament and only want to display the catches you have today? You can do that (for example by applying a filter with the date range set to today). Stars refers to whether the fish has been designated as a starred item in the Live Well. This is easily done by clicking on the star that is over the picture of the fish in the Live Well.