This is like calm water before the wave forms; it’s the state of readiness in which a neuron finds itself before being activated by an action potential.
After crashing onto shore, waves recede back into sea before another can form - this period where no new waves can form mirrors neurons' refractory period after firing an action potential.
Just as waves crash onto shore at specific points, action potentials reach synapses - junctions between two neurons where neurotransmitters are released.