The hydraulic and mechanical components represented on this sketch have been chosen from the Hydraulic and the Mechanical libraries with respect of the wanted design of the system.
Indeed, for this example of a hydraulic jack several types of hydraulic actuators are available and depending on the actual physical system you are able to pick the one that closely represents it.
These hydraulic actuators models are all functional models that can also be modeled on a further approach using HCD (Hydraulic Component Design) in order to get a more advanced physical representation.
These parameters can either be obtained from the manufacturer datasheets, by measurements or calculations (analytical equations) if it is a conceptual design for example.
Plotting the variables is one of the ways that allows you to check if the system is responding properly and to proceed to the needed changes if not. But plots can also be used to compare different designs. The variables that are usually plot for hydraulic components are pressure, pressure losses, flow rates (or velocity).
In this case the requirement for the pressure level at the pump outlet was not to be higher than 5 bars but when you check out the results.