It is easy for most people to understand terms such as "pressure", "quantity" and "flow" because their everyday lives allow them to effortlessly comprehend these terms. For example, people can easily understand that "increasing the flow" while watering their flowers would increase the amount of water coming out of their watering hose, while "increasing the pressure" of the water will make it move faster and stronger through the watering hose.
Electricity terms such as "Voltage" and "Current" are usually hard to understand because people cannot see and / or experience electricity moving through cables and circuits; it is extremely hard for even a cadet electrician to visualize what is happening at molecular level or even clearly understand what an electron is to begin with. Electrons are particles entirely beyond all sensory ranges of human beings, impossible to see or touch; well, except when a ludicrous number of moving electrons run through a person's body, in which case he/she will definitely feel them and experience what is commonly known as an "electric shock".
Still, exposed cables and copper conductors appear entirely harmless to most people just because they cannot see the electrons waiting there to find a way through a low resistance conductor, which can commonly be a person's body, to move towards a lower voltage body, which can commonly be the earth itself.
It is understandable why most people cannot visualize what is happening inside common conductors and cables; even trying to explain that something is moving through copper, a metal, goes against common sense. At the most basic level electricity is not all that different from water, hence its basic terms are fairly easy to understand if you compare an electric circuit to a system of water pipes. The basic difference between water and electricity is that water will fill anything if it somehow manages to burst out of the pipes, while electricity needs a conductor to send electrons to. By visualizing a model system of pipes most people will understand several terms more easily.
Voltage = Pressure – Voltage is pretty much the "pressure" of the electrons and indicates how strongly and quickly they move through the conductors (cables). Voltage and pressure are equal by many respects, including the pipe/cable strength; too much pressure would burst a pipe, too high a voltage would destroy or ignore a cable's shielding.
Current = Flow – Current is the "flow rate" of electrons, indicating how many electrons move through a cable. The higher the current, the more electrons move through the cables. Much like large quantities of water require thicker pipes, high currents require thicker cables.
By keeping the water circuit model in mind a lot of other terms can be explained as well. For example, power generators can be visualized as water pumps, power loads can be pictured as water mills which need flow and pressure of water to rotate and even electronic diodes can be thought of as water valves which allow the water to flow towards one way only.