* CS5 Premium: This was the standard retail version aimed at professional users and individuals. It carried a higher price tag and was licensed for commercial use. The license was typically a perpetual license, meaning you paid once and owned it indefinitely (though updates were not included).
* CS5 Premium Education Edition: This version was specifically designed for students, teachers, and educational institutions. It was sold at a significantly reduced price, reflecting its restricted usage. The license was also typically a perpetual license, but *only permitted use within the educational setting*. Using it commercially would be a violation of the license agreement.
In short: same software, different price and licensing restrictions based on the intended user. The education version is cheaper but only legally usable in educational contexts. CS5 is also very outdated now; Adobe no longer supports or sells it. If you're considering Adobe software, look at their current subscription-based Creative Cloud offerings.