Is Katalon studio better than selenium?

No, but have good features.

Katalon is developed on top of eclipse by integrating selenium appium etc. it is similar to Selenium but in eclipse, you have to create re-usable methods every time such us Take a screenshot, here all the most used methods and codes are built as keyword, and kept inside Katalon. and it is easy to use. we can brought a fresher to production within a week or two with the help of katalon.