What is indicator?
indicator is A variable, with characteristics of quality, quantity and time, used to measure, directly or indirectly, changes in a situation and to appreciate the progress made in addressing it. It also provides a basis for developing adequate plans for improvement. It is a variable that helps to measure changes in a health situation directly or indirectly and to assess the extent to which the objectives and targets of a programme are being attained.
source: A GLOSSARY OF TERMS FOR COMMUNITY HEALTH CARE AND SERVICES FOR OLDER PERSONS. World Health Organization, 2004.