When you create an unsubscribe page you have the opportunity to specify a list of reasons for unsubscribing. So, if your recipient unsubscribes from your mailings, he or she will be able to specify the reason why they are doing so.
After analyzing the reasons for unsubscribing, you will be able to improve your future newsletters. For example, if recipients unsubscribe from your emails because of the excessive amount of mailings, you can reduce the number of outgoing messages.
To specify the reasons for unsubscribing, check "Add an unsubscribe reason survey" when creating the unsubscribe page.
You can choose from the suggested reasons, as well as create your own.
Here is an example of the unsubscribe page with reasons for unsubscribing: