Can someone explain the difference between Judism and Catholicism to me?

I am a catholic, and I used to go to church when I was young but my parents weren’t always extremely religous. They live by the “find God in your own way” theory. So now I’m in college but along with having to deal with figuring out my own religion I also have to figure out other people’s religion. There is a high percentage of Jewish students where I am and the idea behind Judism confuses me!

Last year I was dating (or as close to dating in college as you can get) this guy who grew up in a very religous Jewish family but whenever I asked him questions about his religion he just laughed at me and said I was cute for trying. This left me confused and still without answers.

A friend also tried to explain once the difference between Catholics and Jews but apparently I missed the point and got it backwards. Will someone please explain this “mystery” religion to me, I am still curious!! I want to know the difference beteween Judism and Catholicism