Can you use paid for apps on multiple Apple devices?

Okay, I recently bought the iPad Mini Ret and have spent about £30-40 on apps. I'm thinking of buying the iPad Air but want to know if I can use apps that I have paid for on both the iPad Mini Ret AND the iPad Air at the same time.

So that one day I could play Minecraft on my iPad Mini Ret and the next my iPad Air?

If I were to use my Apple ID on the iPad Air will it allow me to download the apps I have paid for?

I'm just worried because I don't want to have to re-buy everything since I've already done that as I bought a bunch of apps on my Android device and had to re-buy the same apps on my new Apple device.

Added (1). Is there a limit to how many times you can do this?

Yes you can, if you sign in with the same account you can download all the apps you have paid for unless you had already got a refund. It doesn't work with Apple and Android devices together because they are two different companies. I once deleted an app 3 years ago on my iPod and I got it back on my iPhone a week ago without repaying. Don't worry.

Also there's no limit to how many times you can do this, as long as each device is logged into the same apple account

Yes. Once you buy an app, it's YOURS! You can download it as many times as you want and on as many devices as you want.