What aws should I take for my app

I have an app on bubble and i will have to store a lot of staff and companies documents so i created a account amazon web service to link it to my app by using zeroquode plugin.
But I am bit confused by the tons of products I see on amazon and don’t know which one to take. It seems that aws s3 is the one to take.
Please help me understand in a simple way these products and the one you recommend.