What is the difference between strut channel, C channel and U channel?

Strut channel is a specialized support profile with inward lips and an open slot designed for channel nuts and strut fittings. C channel and U channel are broader shape descriptions based on the cross-section. It is useful for solar brackets, photovoltaic support, pipe support frames, conduit supports, equipment frames and structural support systems. The slot design should consider bolt size, anchor position and channel strength.
In many solar, construction and MEP projects, buyers may search for slotted C channel, galvanized U channel, C strut channel, or U strut channel when they actually need a compatible strut support system.