An overview was made of dry matter (DM) and quality losses that occur during the ensiling process. The aim was to review the current knowledge on the course of the fermentation pathways in various raw materials and the loss of DM accompanying this process. This review discusses the main groups of microorganisms involved in the ensiling process, the accompanying fermentation patterns, and the resulting DM losses. The possibility of reducing DM and quality losses during the ensiling process in practice is presented. The paper concludes with future perspectives and recommended management practices to reduce losses over the whole ensiling process.