Differents between keeping images

I presume you're talking about the JPEG Options: Baseline ("Standard"), Baseline Optimized and Progressive.

The JPEG format was introduced at around the same time the first web browsers were being developed. Some of these early web browsers only supported the Baseline version of the JPEG format. All modern browsers support the Baseline Optimized version, which means you can squeeze out a few more KB in file size by choosing that option if you wish.

The third option, Progressive, is a little more interesting... back in the early days of the Web when most people had slow connections, using Progressive JPEGs was a neat way of getting the images to display gradually instead of having to wait for the whole image to load before they were displayed in the browser. Unfortunately, Internet Explorer didn't support Progressive JPEGs for a long time, so their use diminished when people stopped using Netscape Navigator (and connections got faster). They've enjoyed a resurgence in recent years as web developers have had to think about download speeds again, with many people around the world not having particularly fast connections on mobile devices.