Biochar is a solid material obtained from the thermal decomposition of biomass of diverse biological origins through a process called pyrolysis. Biochar has great potential for reducing greenhouse gas emissions, sequester carbon in the soil, rehabilitate degraded soils, and reduce dependence on chemical fertilizers in crops. It also improves the physical, chemical, and biological properties of the soil and has a positive effect on plant growth. Given these attributes, there is a growing interest for adopting its use in agriculture, soil and land reclamation, and climate change mitigation. The effects of biochar application can be neutral or positive and will be determined mainly by factors such as the origin of the raw materials, carbonization conditions, frequency of applications, the method of application and dosage. In this review, we offer a detailed examination of the origins of biochar and the technologies used for its production. We examine the various materials that have been used to produce biochars and how they affect their physico-chemical characteristics, and we describe their applications in agriculture and climate change mitigation. Finally, we list the guides that describe the standards for the production, characterization, and commercialization of biochar that seek to guarantee the quality of the product and the essential characteristics for its safe use.