What is CloudFront ?
CloudFront is a web service that speeds up distribution of your static and dynamic web content, for example, .html, .css, .php, and image files, to end users. CloudFront actually is a CDN [more on CDN]
How it works ?
CloudFront delivers your content through a worldwide network of edge locations. When an end user requests content that you're serving with CloudFront, the user is routed to the edge location that provides the lowest latency, so content is delivered with the best possible performance.
If the content is already in that edge location, CloudFront delivers it immediately. If the content is not currently in that edge location, CloudFront retrieves it from an Amazon S3 bucket that you have identified as the source for the definitive version of your content.
[Create your own CloudFront]
[Managing Assets on Amazon CloudFront]