CloudFront is the Content Distribution Network (CDN) service offered by Amazon Web Services (AWS).
This service allows you – whether or not your site itself is hosted in the AWS cloud – to offload static content to one of AWS’ distributed network of sites, to load faster for your visitors, by being served from a (really fast) server located near to them, rather than being sent from your server sitting wherever that happens to be.
Because CloudFront is optimized to quickly deliver static content, it will usually be a faster way to send images. Because its got locations caching your static content in multiple regions across the globe, you’ll be able to faster serve visitors from anywhere.
Also see other CDN services, like CloudFlare (which also provides a DNS proxy service too, and is free).