The Membership Pro - GeoIP plugin is used to auto-detect user country base on his IP uses service provided by https://ip-api.com/ . That helps select the right country for visitors when they access to subscription form of a plan. It is useful if you provide subscriptions to international subscribers, especially if the price depends on country (for example, tax rate depends on country).
If you want to use this useful feature, go to System -> Plugins, find and enable Membership Pro - GeoIP plugin