How do I talk to a guy who wants to "catch up" and what does that mean?

I am defiantly an introvert when it comes to striking up a conversation with new people. How do I talk to a guy who wants to “catch up” and what does that mean? I’ve known of this guy for a while. I don’t want to come across as a “try hard”. How do I turn off my flirt, and keep myself from over fantasizing? I just want to have a normal conversation that flows without getting nervous, but still be interested and fun.

[Hears the backstory, we went to elementary together. Lawrd! Forever ago, I know. I transferred schools in middle school, so I went from small town to smaller town. I would always go back to my home town at least twice a week to go shopping and whatever else my parents had planed. I do remember spotting him a few times at public events, but never actually said, “Hi.” or had a conversation. Boys were the last thing on my mind at the time. We did have a handful of mutual fiends but I rarely hung out with them. He reached out to me our junior year of high school, we texted a bit, but of course I had no experience in the flirting department at that time. I guess you could say I bloomed sort of late. I do remember him telling me he used to have a crush on me back when we went to school together. It’s been a while back, but if I remember correctly we quit texting when he got a girlfriend. From what I’ve been told they were together a couple years into college. By that time I’ve already forgot all about him and have been living my own fun life. Being out on my own making friends and experiencing life. I’ve never obsessed over him. He has moved back to the area and I am starting to get excited since after all these years he has reached out to me a second time and wants to “catch up”. Needless to say I have gained more social skills but I am still nervous and afraid my shyness is going to come out and I wont be able to have a good conversation with him.]