The word mushroom may mean different things to different people in different countries. Specialist studies on the value of mushrooms and their products should have a clear definition of the term mushroom. In a broad sense, “Mushroom is a distinctive fruiting body of a macrofungus, which produce spores that can be either epigeous or hypogeous and large enough to be seen with the naked eye and to be picked by hand.” Thus, mushrooms need not be members of the group Basidiomycetes, as commonly associated, nor aerial, nor fleshy, nor edible. This definition is not perfect, but it has been accepted as a workable term to estimate the number of mushrooms on Earth (approximately 16,000 species according to the rules of International Code of Nomenclature). The most cultivated mushrooms are saprophytes and are heterotrophic for carbon compounds. Even though their cells have walls, they are devoid of chlorophyll and cannot perform photosynthesis. They are also devoid of vascular xylem and phloem. Furthermore, their cell walls contain chitin, which also occurs in the exoskeleton of insects and other arthropods. They absorb O2 and release CO2. In fact, they may be functionally more closely related to animal cells than plants. However, they are sufficiently distinct both from plants and animals and belong to a separate group in the Fungi Kingdom. They rise up from lignocellulosic wastes: yet, they become bountiful and nourishing. Mushrooms can greatly benefit environmental conditions. They biosynthesize their own food from agricultural crop residues, which, like solar energy, are readily available; otherwise, their byproducts and wastes would cause health hazards. The spent compost/substrate could be used to grow other species of mushrooms, as fodder for livestock, as a soil conditioner and fertilizer, and in environmental bioremediation. The cultivation of mushrooms dates back many centuries; Auricularia auricula-judae, Lentinula edodes, and Agaricus bisporus have, for example, been cultivated since 600 ad, 1100 ad, and 1650 ad, respectively. During the last three decades, there has been a dramatic increase in the interest, popularity, and production of mushrooms through farming worldwide. The cultivation methods can involve a relatively simple farming activity, as with Volvariella volvacea and Pleurotus pulmonarius var. stechangii (=P. sajor-caju), or a high-technology industry, as with Agaricus bisporus, Flammulina velutipes, and Hypsizygus marmoreus. In each case, however, continuous production of successful crops requires both practical experience and scientific knowledge. Mushrooms can be used as food, tonics, medicines, cosmeceuticals, and as natural biocontrol agents in plant protection with insecticidal, fungicidal, bactericidal, herbicidal, nematocidal, and antiphytoviral activities. The multidimensional nature of the global mushroom cultivation industry, its role in addressing critical issues faced by humankind, and its positive contributions are presented. Furthermore, mushrooms can serve as agents for promoting equitable economic growth in society. Since the lignocellulose wastes are available in every corner of the world, they can be properly used in the cultivation of mushrooms, and therefore could pilot a so-called white agricultural revolution in less developed countries and in the world at large. Mushrooms demonstrate a great impact on agriculture and the environment, and they have great potential for generating a great socio-economic impact in human welfare on local, national, and global levels.