The custom voting and star rating options allow you and your team to collectively add inputs on your app items. The star rating lets anyone with access to the item rate the item from one to five stars, while custom voting is a more customizable field that lets you add various options for your team to vote on.
To enable either of these options, go to your app template, then click the wrench icon that appears in the upper right of the field selection pane. You'll find the custom voting and the star rating options from here.
All votes entered in these fields will be collected and displayed on your app item, so you can use this to gather opinions or even to hold a vote to make a team decision.