Pyrolysis and gasification processes, the two most widely used processes of energy conversion from biomass have been practised by mankind from time immemorial. However, it is after the crude oil crisis, the research world envisaged that these processes are very important to extract energy through alternate means of energy recovery from biomass. As the study on pyrolysis and gasification is enthralling and offering bright scope, many researchers have started to work on pyrolysis and gasification. Thus, the need of the hour is to disseminate some basic fundamentals about pyrolysis and gasification processes in order to provide a basic understanding to the peer and successive researchers. With this intention in mind, the current article discusses about the process, reactions and formulae involved in pyrolysis and gasification processes. The article also throws some light on the classification and controlling parameters of pyrolysis and gasification processes.