Ipad

Unless you are purchasing an iPad using finance, there are no ongoing monthly payments for the iPad itself. All iPad models are available as either WiFi Only, or WiFi+Cellular.

WiFi Only models can only connect to WiFi networks - or to a wireless hotspot of a mobile phone (or wireless router) for internet access when you are away from WiFi.

WiFi+Cellular models also connect to the internet using WiFi - but also have capability to be used with Cellular networks, should the need arise, without reliance upon a mobile phone hotspot connection. Choosing a WiFi+Cellular model iPad does not commit you to arranging cellular service, but does provide the additional flexibility to do so if the need should arise. These models can also connect via a mobile phone hotspot.

When using WiFi+Cellular models with a Cellular network provider, you have many options. Some Carriers offer pre-pay plans, others may offer a contract with monthly payments for service. You can also activate short term cellular service directly from the iPad using the iPad’s built-in eSIM:

Set up cellular data service on your Wi-Fi + Cellular model iPad - Apple Support

Be aware that an iPad, whether a Cellular model or not, is not capable of directly accessing Cellular Voice or SMS/MMS Messaging features. An iPad with either WiFi or Cellular connectivity alone can only access IP-data services. If you have added a DataSIM or activated the eSIM with Cellular plan to a WiFi+Cellular model of iPad, the number associated with the DataSIM/eSIM is only used to identify your account for billing purposes. This number is not (and cannot be) used for making calls or sending messages.

only if you buy the cellular model and get a carrier contract it it

if you do that then you get internet from the cellular network rather than having to depend on wifi, you do however not get the ability to make voice calls or sending sms's