Historically, the following schematic symbol attributes are used for PCB layout:
attached to a symbol, defines a PCB element file name to be placed on the layout for that instance of the symbol. PCB element is a visible pattern, the footprint, corresponding to a physical electronic component in PCB layout.
attached to a symbol is its reference designator on the schematic. In PCB layout programs, it can appear as the displayed element name.
usually is used to store the type of the electronic component representing by a symbol, e.g. 7400, or its value, e.g. 1K for resistor. In PCB layout programs, it can also be shown as element name depending on their settings.
All the above attributes are used to propagate the changes in your schematics to the corresponding PCB layout.