In many parts of the KiCad system, there is provision to store data in a "value" field.
The name "value" makes the most sense for something like a resistor: It will have something like "1k" (for 1 kilo-ohm) in it in a "proper" project.
Some other things, for example a switch, do not so obviously have a use for a "value" field, but it can still do good work. For example, the "value" field you might be used to associate a part number with something.
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