The end result is the same as hosting on S3 + CloudFront, it just saves you a lot of trouble setting things up, makes things just work, gives you nice features like lambdas, A/B testing, forms, authentication, etc etc for free, and just makes your life super easy.

Basically, if you have a repository with your Jekyll (or whatever) site, just add it to Netlify and that's it. It's served, and will automatically update when you push.