Signals may be scalars, vectors, or busses. They may carry data or control flows.
You use signal labels to make model functionality more understandable from the Simulink® diagram. You can also use them to control the variable names used in simulation and code generation. Enter signal names only once (at the point of signal origination). Often, you may want to also display the signal name elsewhere in the model. In these cases, the signal name should be inherited until the signal is functionally transformed. (Passing a signal through an integrator is functionally transforming. Passing a signal through an Inport into a nested subsystem is not.) Once a named signal is functionally transformed, associate a new name with it.
Unless explicitly stated otherwise, the guidelines in Signals apply to all types of signals.
For more information about the representation of signals in Simulink models, see Signal Basics in the Simulink documentation.