It has been historically challenging for researchers and others to rehabilitate damaged soils, such as those that have been chemically treated, used for infrastructure or mining, which can be costly, time-intensive, and invasive. Especially, in recent years, biochar has not only emerged as an attractive alternative, but also a cost effective and sustainable one. The carbonaceous material produced by the pyrolysis of biomass in the absence of excess oxygen is carbon rich and confers several benefits. By retaining carbon in the soil, soil carbon sequestration through biochar has potential climate change mitigation benefits and may also contribute to enhanced soil fertility and structure. This paper focuses on numerous applications of biochar in soil improvement including nutrient immobilization, pH control, and healthy microbial population stimulation. Via wear sorption, precipitation, and electrostatic interactions, biochar can immobilize contaminants, but also be a carrier of specific species of microorganisms. Importantly, these factors (feedstock type, pyrolysis temperature and heating time) are interwoven with the properties of biochar and their use.