These were typically in the shape of long tubes but with the focus on increased energy efficiency they have been made into other shapes to replace the standard incandescence light bulbs.
Standard fluorescent lighting comes in multiple form factors, including the T5, T8 and T12. The brightest version is the T5. The T8 and T12 are less powerful and are more suited to plants with lower light needs.
The type of phosphor material used in the bulb affects the spectrum of light that fluorescent bulb produces.
Many folks use fluorescent lamps to supplement their indoor lighting requirements. An electric current in the gas excites mercury vapor contained in the bulb, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow or product light.