The frequency at which this wave oscillates between the two depends on the distance between them, which in turn is directly related to the bending of the spring element (and therefore the weight of the object on the platform).
This wave is picked up by the transmitter, sent to the receiver where it is amplified, and the passed back to the transmitter to create a feedback loop.
Dirt, water and other substances can easily damage the connectors on the board, which makes your entire scale less reliable and more likely to need repairs in the future.
So if you order from a source that does not adjust or group the load cells based on the identicalness of their outputs, you’ll have to manually adjust the load cells on your own.