The world’s population is increasing at an alarming rate and to feed this population, food production needs to be increased significantly. There are several abiotic and biotic factors affecting the productivity of crops. Among biotic factors, weeds are the most important constraint to crop production throughout the world. They cause a huge yield loss in different crops and cost growers a significant amount of money. Herbicides are widely used to control weeds; however, there are concerns over the evolution of resistance in weeds, limited availability of herbicides with new modes of action, and environmental pollution. These issues suggest the need to reduce reliance on herbicides and develop sustainable weed management programs. However, to develop such programs, there is a need to gain a better understanding of weed biology. This article briefly describes the importance of weed biology in managing weeds.