Informatics is an important field of practice and study. It is very similar and also close to Information Science. Informatics initially only were considered as a branch of advanced applied science but gradually it has become a domain centric field for information and technological solutions. Among the most common and available Informatics nomenclature important are Health Informatics, Bio Informatics, Geo Informatics, etc. The advent of IT and Computing in the field of Environmental Sciences and the whole sector leads Environmental Informatics as an important interdisciplinary field of studies and practice for environmental monitoring and solutions leading to the environmental management, disaster management, agricultural management. Therefore, universities and educational institutions are moving towards academic programs on environmental informatics and allied fields. Similar to Environmental Informatics another sub field also gaining popularity i.e., Agricultural Informatics and this is incorporated with the technology and management also. The subject is being offered at different level for the best environmental solutions. Moreover, another important domain centric Informatics field also becomes important i.e., Social Informatics which is dedicated to social applications using Information Technology and allied systems. Social Informatics is also concern about the Urban and Rural Development with the Urban and Rural Informatics. This paper is a theoretical study on Environmental, Agricultural, and Social Informatics with reference to basic features, functions, and applications.