Unlike classes, structs are by default copied instead of referenced. Typically, you use structs to design small data-centric types that provide little or no behavior. For example datetime is implemented as a struct: https://learn.microsoft.com/en-us/dotnet/api/system.datetime

public struct Coords
{
    public Coords(double x, double y)
    {
        X = x;
        Y = y;
    }

    public double X { get; }
    public double Y { get; }

    public override string ToString() => $"({X}, {Y})";
}

readonly

Because structure types have value semantics, it's common to define immutable structure types. This can be done with the readonly modifier.

public readonly struct Coords
{
    public Coords(double x, double y)
    {
        X = x;
        Y = y;
    }

    public double X { get; init; }
    public double Y { get; init; }

    public override string ToString() => $"({X}, {Y})";
}

usage

var location = new Coords(2, 4);
Console.WriteLine($"location.X, location.Y");

Because a struct is a value type rather than a reference type you cannot have a null struct. Each field will use it's zero value, which would be null for any reference fields.