The simulation shows a charge distribution between which there is a (nearly) uniform electric field (like the field between the plates of a capacitor) and a test charge (the small red dot in between the two rows of charge). The field vectors and equipotential lines are drawn for this case. The test charge shows a vector with the net force acting on it.
Move the test charge around and note the direction of the force acting on the test charge.
Which direction does the force on the test charge point relative to the electric field vectors?
Which direction does the force on the test charge point relative to the electric equipotential lines?