You've stored related data in separate variables. Maybe a student's name in one string, their grade in an integer. When you need to pass all three to a function, you pass three parameters.
With ten students, you manage thirty variables. Structs let you group related data into a single package. Define what belongs together once, then treat the group as one unit. One student variable holds name, grade, and ID.
Pass one thing instead of three. I'll show you how to define custom types, create variables from them, access their members, and organize data so your code doesn't drown in scattered variables.