The circuit essentially just makes a copy - at the output - of the the input voltage, V_in.  It does that without drawing any current from wherever the input voltage terminal is attached.  However, at the output terminal you can draw whatever amount of current the operational amplifier can supply (and that depends upon the kind of operational amplifier you use).

        There are many situations where you do not want to draw current from a circuit (i.e. "load" the circuit).  Some of those situations are:

• A bridge circuit or a voltage divider circuit - maybe where there is a resistive sensor in the bridge or voltage divider - and drawing current when you measure the voltage would be enough to change the voltage.
• A rectifier/filter where the output is across a capacitor.  In that situation drawing current from the capacitor will discharge the capacitor, reducing the voltage.

      If the difference between V₊ and V_- is negligibly small so that V₊ = V_- we must have:

• V_out = V_in

        Here is a drawing of what the circuit should look like on a circuit board.  In this drawing we have shown connections that are actually made under the board - connections that are not visible from the top of the board.  Those are shown with lighter lines that go through the connecting "holes" in the drawing.  They are there to show you how the various wires are actually connected to the operational amplifier through metallic connections under the board.