I did not understand robustness

Robustness is a property that certain systems have, which can be summarized as the capability of exhibiting a certain desired behavior despite variability in their components or disturbances. In the example at page 10 of Lecture 1-1, for instance, the final velocity of the vehicle under the action of the feedback controller does not depend on its mass, friction nor controller gain, if the gain is sufficiently large.

--Elisa