An R–2R Ladder is a way to perform digital-to-analog conversion, using repetitive arrangements of very precise resistor networks in a ladder-like configuration. They don't have a conventional dac-chip.
For a 10-bit converter, even using 0.1% precision resistors would not be sufficient. High resolution R-2R ladders formed from discrete components, the nonlinearity is corrected. The more advanced the correction method is, the better the performance.