It means you need an available wifi connection to get online. Some model ipads can be activated on the networks of most cell phone companies and use a data plan to access the internet. This model is not capable of being activated for cellular use.
This particular iPad does not have the capability to connect with a cellular system, its only means of getting on the Internet would be via a wifi system such as your home system or a hotspot from your phone.
There is a different model that has a cellular chip in it to access the internet without having to connect to WiFi. It costs more and you must pay for monthly data this one requires an internet connection through WiFi to access things not on the device.