what file format(s) will be if purchase ebooks from Kindle for Android app?

Anybody know what file format(s) will be if purchase ebooks from Kindle for Android app?

Will it happen, I purchased and downloaded the ebook into my tablet however the ebook can not be read because my tablet do not support a specific file format?

Did Amazon make perfect compatibility already, whatever you can purchase from them, you will be able to read?

I have purchased a few books and it is no problem to be read. But curiosity.

Thanks asnwer pal