Engineering change orders (ECOs) are modifications to an implemented design, with the intent to minimize impact to the original design. The Vivado Design Suite provides an ECO flow, which lets you modify an existing design checkpoint to implement changes, run reports on the changed netlist, and generate the required bitstream files.
The advantage of the ECO flow is fast turn-around time by taking advantage of the incremental place and route features of the Vivado tool. The Vivado IDE provides a predefined layout to support the ECO flow. Refer to this link in the Vivado Design Suite User Guide: Implementation (UG904) for more information.