Warping: Warping is the distortion of a part as it cools and shrinks unevenly, lifting corners off the build plate or bending flat faces out of shape.
Most materials shrink as they cool. When one region cools and contracts before another, internal stress pulls the part out of shape. In FDM, warping shows as corners lifting off the bed, worst with ABS, nylon and large flat parts. SLS and MJF parts can warp if they cool too quickly or unevenly; metal printed parts warp from residual stress unless they are anchored and stress relieved. Moulded and cast parts have the same problem, controlled through even walls and cooling.
What it means for the price
Warp-prone parts carry risk: a failed or out-of-tolerance print costs the machine time a second time. Shops offset that with an enclosed printer, a brim, slower printing, a different material or orientation, or a risk allowance on difficult geometry. A large flat plate in a high-shrink material is a classic part to quote with care.
Example: a flat ABS panel 200 mm across is far more likely to lift at the corners than a 40 mm cube of the same material. The figures are an example.
Common confusions
Warping is not anisotropy: one is about shape, the other about strength. Nor is it the small, even shrinkage that a shop scales the model to correct. Read design for 3D printing for shapes that resist warping.
Go deeper: Design for 3D printing: walls, overhangs, holes, clearances and orientation