What does a smile and wave mean?

I've known this guy for probably over 10 years. But we were never close and I'm only not sure if we've ever had an actual conversation. I saw him today for the first time in over a year. From across the room we locked eyes. I smiled, and he just stayed looking at me. Later in the parking lot, we just so happened to park facing each other. We both turned on our cars and he locked eyes with me again and waved. I smiled and waved and he smiled back.

We've never spoke, but today he looked really excited to see me. What does that mean?
What does a smile and wave mean?
Post Opinion