The parade is held every year, to celebrate the nearing of their university graduation. Those on the trucks are two years away from graduation, while those walking with the funny hats are on the last year. The others are there just for the fun.
The parade starts on the university campus and slowly passes through the city streets, until it reaches downtown. At the end of the day, there's concerts near the river and other activities.
This is a bit far from the city I live in and as I had a previous engagement, I had to leave early. So apart all other constraints, I had to work in a hurry (sort of).
I hope I'll do better next year, having your comments in mind and my own evaluation. All in all, it was yet another fun learning experience.