Quota sampling is a type of judgment sampling in it quotas are set according to some characteristics of the population.
These characteristics could be income groups, age, religion, political party, race, caste, amount to be spent on an item, number of programmes watched on TV, number of people checking into a hotel during the off-season, tourist stops receiving most of foreign visitors etc.
The researcher arranges some interviewers who are given some quotas. Each interviewer is supposed to select some elements for his sample; this number is quota. Within this quota, the interviewer can select the sample on the basis of personal judgment.