Using clones - cuttings from the cannabis mother plant - saves some time compared with growing them from seeds. It also allows for the new plants to be exact, genetic copies of its parents - a characteristic that is very convenient for many breeders, that are trying to find their Holy Grail of marijuana.
Fresh clones are extremely fragile and require extra care during their first days or even weeks. High humidity and rooting enzymes makes wonders. Until they start showing signs of adaptation, creating new layers of leaves, clones are best kept in a propagator. Those come in a variety of sizes, some with heated beds, to pamper your young plants that will return the favour in terms of juicy harvest.
Lighting during the first stage of clones' lives is a controversial matter - some growers prefer to limit the amount and intensity of light exposure, as cuttings are very delicate, while others give their plants 24 hours of light for the first few days, if often at a limited intensity (CFL, MH at a greater distance, LED).