When the movement moves, there will be a crisp percussion sound, the click holds the ratchet wheel against the force of the mainspring, allowing the watch to be wound. It's name is well suited, as the clicking noise you hear when a watch is wound is the click impacting each tooth of the ratchet wheel. Some clicks have a separate click spring that forces the click back into contact with the ratchet wheel's teeth. Others have the spring integrated into their design. Their design can vary widely, and often are a matter of movement architecture style.
The first step in disassembling a movement is to let down the power of the mainspring. This action requires the click be held back from the ratchet wheel, and the winding stem let turn backwards.