What is the API for AWS S3... I'm using AJAX to Get/Post

I'm building an app using ionic framework and I want to implement the Amazon s3 for storing crowd-sourced images in my app.

I have done researched and I already know hot to create a bucket and a folder. 2 things i need to know

1. URL for Ajax GET/POST request
2. What is a good way to map amazon S3 stored images to its appropriate user_id in my db