Difference in Amazon S3 storage types; Standard, Reduced Redundancy and Glacier? What is cloud front?

Thinking about starting a image upload service on my website with PHP where users can upload their photos. Have found Amazon S3 http://ift.tt/GYAlz3 and I think it is a good solution for storing pictures. But Iam be confused about the different storage types

Standard Storage

Reduced Redundancy Storage

Glacier Storage

Have tried to read on the site but does not become wiser. Is it how often I want to access the data? Glacier just seems to be for backup if you don't want to access the data very often and Reduced Redundancy is the same as standard but without the secure connection? Can someone briefly explain the difference between them and what fit best for me (a website/service where users can upload photos).

Have also read that people recommend using CloudFront with Amazon S3 http://ift.tt/m2049N. What is it good for? Can anyone explain why? It's the same here, have tried to read on Amazon but

give developers and businesses an easy way to distribute content to end users with low latency, high data transfer speeds, and no minimum usage commitments.

even if it sounds good does it not tell much what it is.