Records: data that compares by contents

The class equality trap

class PointC { public double X, Y; }
var a = new PointC { X = 1, Y = 2 };
var b = new PointC { X = 1, Y = 2 };
// a == b is false! a.Equals(b) is false!

Reference types compare by identity by default: two separately built objects are never equal, even with identical contents. Overriding Equals/GetHashCode correctly by hand is subtle and easy to get wrong.

Records do it for you

record Point(double X, double Y);

var p1 = new Point(1, 2);
var p2 = new Point(1, 2);
Console.WriteLine(p1 == p2);        // True
Console.WriteLine(p1.Equals(p2));   // True
Console.WriteLine(p1);              // Point { X = 1, Y = 2 }

A record generates value-based Equals, GetHashCode, a readable ToString, and an immutable-by-default shape. It's the right default for data you pass around: messages, coordinates, line items, query results.

with copies-and-changes without mutating:

var moved = p1 with { X = 10 };   // new record: (10, 2); p1 unchanged

Immutability plus value equality is exactly what "a piece of data" means — which is why records exist.