i insert my regular sim in my ipad but not recieving calls or messages

To expand upon ShagCA's comment, the iPad SIM slot is intended for installation of a "suitable" dedicated DATA SIM, from a Cellular Carrier, to provide data-only services over a cellular network.

Per Borg529's comment, the iPad is not a phone - and does not provide the same features. Using Continuity features of iOS, your iPad can access calling features of an associated iPhone IF your iPhone Calling plan allows it.

thank you.but what is the use iPad SIM card slot for iPad Air 2.

Data or access to the internet.

Generally, you cannot use a regular "phone" SIM from your phone with an iPad. iPad's require installation of a data-SIM - as phone features of your calling plan cannot be applied/used on your iPad.

To make or receive phone calls from your iPad, you also require an iPhone. Dependent upon your Cellular Carrier calling plan, you may be to make phone calls from your iPad (using the FaceTime App), or directly via WiFi Calling.

iPads not a phone, it will not make, or receive calls. You need iPhone, and use “Continuity,” to send and receive text messages from iPads.