What does 'representativity' mean in case of a sample?

The word 'representative' means that people within the sample do not only represent themselves but a larger group as well. The fact that the people polled really represent the group under study well can be assured by, on the one hand, the way of selection (sampling) and, on the other hand, the success of the data collection. The data obtained from a representative survey are not absolutely exact as we only collect data from members of a sample.