CloudFront is a web service by Amazon that resembles in functionality to a CDN (Content Delivery Network). Amazon supports 16 different locations worldwide for edge content distribution. You upload your content once and your users will retrieve your content from a location which is closest to them. This obviously increases content delivery performance. The entire infrastructure is managed and supported by Amazon.
From Amazon website:
Amazon CloudFront is a web service for content delivery. It integrates with other Amazon Web Services to give developers and businesses an easy way to distribute content to end users with low latency, high data transfer speeds, and no commitments.