Understanding the negative impacts of using chemical fertilizers on living organisms and the environment, in general, has encouraged finding natural alternatives. Hence, biofertilizers are applied through soil or seed and are prepared from promising microbial strains (living or dormant cells) that help economically important plants in taking nutrients by interacting with their rhizosphere. Fungi are famous contributors in this field due to their ability to live in different ranges of environmental habitats and carry out processes such as nutrient cycling and decomposition of organic matter. However, many types of interactions were reported between fungi and other organisms as ants or microorganisms as bacteria. In this review, we focus on understanding what biofertilizers are, how they act and what type of interactions are noticed among them. Moreover, the classification of biofertilizers and some of their carriers are highlighted. Furthermore, we introduced examples of some fungal genera that are used as promising biofertilizers.