What should I expect when I go to a synagogue next week?

Hi, I want to start of by saying that I'm in my teens and that I'm not Jewish. In fact I currently go to a catholic school. I feel no connections or religious attachments to being catholic. I love learning about new religions and I'm fascinated by Judaism. I wrote to the rabbi of a conservative synagogue asking him if I could attend Shabbat, and he wrote back that I was perfectly welcome to attend. So my question is, what's it like for a gentile to got to a synagogue and what should I expect. Any tips are welcome. Thanks.