Is a structure in a programming language a value type or a reference type?

In C#, a struct is a value type, not a reference type.

This means that when assigning or passing a struct to a method, all its data is copied, rather than passing a reference to the object in memory, as is the case with classes (reference types).

Example:

struct Point
{
    public int X;
    public int Y;
}

Point p1 = new Point { X = 1, Y = 2 };
Point p2 = p1; // a copy of p1 is created
p2.X = 10;
// p1.X remains 1, since p2 is a copy

This behavior is important to consider when designing and optimizing applications in C#.