The decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition.
Dead plant remains such as leaves, bark, flowers and dead remains of animals, including animal faecal matter, constitute detritus, which is the raw material for decomposition.
During decomposition, the detritus is digested by the enzymes released by microbes, like bacteria, fungus, etc. Decomposition is faster in humid condition and on cellulosic material.