The long answer(s) can be found by searching the Web for "baseline standard", but here's what you need to know about PSE's JPG saving options:
JPG is a "lossy" method of compressing image files -- it throws away image data before doing the compression, so set your "Quality" option to "Maximized". That is the key setting for image quality.
"Baseline (Optimized)" might reduce file size slightly (2% or so), and might be incompatible with viewers using old technology. "Optimized" might produce better colours, but that might not be perceptable.