I have an android phone that I want to put pictures in my apple iPad how can I do this? What is an iCloud?

If you owned an iPhone this would be simple. But Android and iOS don't speak to each other. So, the best option would be to upload your Android photos to your photo files on your home computer, then sync the photos from your computer to your iPad using iTunes.

iCloud won't help you in this situation, because you'd need an iPhone, which would then sync content between your iPhone and iPad seamlessly. But you don't own an iPhone, so iCloud isn't really a service that will do that in what you want to do here.

Once the photos are on your computer, this link will explain how to sync content from your computer to your iPad --> Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support

Learn more about iCloud at https://support.apple.com/guide/icloud/what-is-icloud-mm74e822f6de/icloud. iCloud will not work with an Android device. As @lobsterghost1 mentions, you'd need to transfer your images to a computer first.