What do braces after C# new statement do?

Given the code below, what is the difference between the way position0 is initialized and the way position1 is initialized? Are they equivalent? If not, what is the difference?

class Program
{
    static void Main(string[] args)
    {
        Position position0 = new Position() { x=3, y=4 };

        Position position1 = new Position();
        position1.x = 3;
        position1.y = 4;
    }
}

struct Position
{
    public int x, y;
}