You get what you pay for. I have one, I know.
For $99, you get a basic 10" tablet and keyboard. It is great for email, casual web browsing, reading ebooks, listening to music or audiobooks (headphones/earbuds highly recomended) and light word processing. You can also watch videos (movies, TV and YouTube), but the picture quality isn't great.
You can also keep your calendar, contacts and to-do list, use various calculators, play chess, solitaire and other low-graphics games, plus much more. That's because you also get full access to the Google Play Store, where you can download literally 1,000s of Android apps. (Amazon Fire tablets have a much smaller store.)
With Android 9, you can configure your tablet to automatically store most apps and files on a microSD memory card so you won't run out of space. I recommend that you install at least a 32 GB card to store files. I bought a 128 GB card for mine.
The ONN tablet is not fast and its battery life is short, but it works. What do you expect for less than $100?
What you DO NOT get is a fast flashy gaming machine. Don't expect one for only $99. The cheapist iPad is $350 (without the keyboard) and it may not suit your needs.