Two ended arrow connedting two Vin or Vout points?

[SusiKette]

If you look at the picture below, you see that Vin and Vout connect two points with arrows. What exactly do the arrows mean?

 

[Harald Kapp]

Welcome to EP.
These arrows indicate that Vin and Vout, respectively, are connected between the two circles (input and output). The bidirectional arrow is typically used in anglo-american based designs. In Europe it is much more comon to use a single arrow to indicate the (assumed) direction or polarity of a voltage (useful for setting up wquations for node analysis of a circuit).

 

[Wireaddict]

These arrows are somewhat analogous to dimension lines on a mechanical drawing showing the distance between 2 points, only on a schematic the arrows & descriptors show the signals or power in some cases & the terminals.