Hi, is it possible to have 2 phones that have 2 different numbers?

Let's say I have an iPhone, but I want an Android phone. Is it possible to carry 2 different phones with the same carrier (i.e. phone number), or will they have two different numbers that are in the same company let's say AT&T. Will I have to pay for extra fees (subscription to that phone company line thingy)? What if I don't want a phone number for the Android phone. Will that work? It will still be connected to the Internet (wifi, LTE extended network), but it won't have phone number bc it's used for other reasons. But if I did get a phone number for that one without changing my iPhone's number, will that work, too? What if I have 2 different numbers & paying the same company AT&T for both? Does that work, or does it have to be the same model of phone? I'm new to this and want to see how this works. I know this is a lot and so many scenarios. Please bear with me as it's my first time, but I've never had to pay for my own personal phone until I'm working. It's really on my mind for the future. Thanks in advance. Also give more scenarios, if I'm missing something. Can I pay in on the spot (full) for the WIFI thing on the phone AND the phone company AT&T or T-Mobile or something? I know it's diff for every single one of them but give specific examples, thanks!