Both are cloud storage spaces, where you can store your files outside your devices and can access then from anywhere, anytime to any of your devices. One drive belongs to Microsoft while Google drive belongs to Google.
It depends on your usage, (just like Bino said) Google drive is necessary and most comfortable for android users, who usually deal with lots of Google apps and products. It will be easy to reach the drive. On the other hand, Onedrive also is fine when using their products also. So I advise you to get used with both. Especially, because they both have storage limits (~15GB) if using without payment.
