The saturated vapor pressure of a substance is the pressure, which is caused by the saturated vapor of the substance.
How Is The Explanation?
When a liquid (eg water) in a container is left in the open air, it will run out. This happens because the water evaporates. At normal temperatures (not at the boiling point of water), evaporation occurs only on the surface of the liquid. This occurs because the surface is the part closest to the outside air so that the water particles on the surface have the greatest chance of leaving the liquid phase into the gas phase (evaporates).
The higher the temperature, the faster the evaporation occurs, whereas the lower the temperature, the evaporation also progresses more slowly. If the container containing this water we are sealed so that no water vapor can be released into the open air, then the vapor will be trapped in the space between the lid of the container and the water surface.
This evaporation will continue until one day, the space is "crowded" by water vapor. This situation inhibits further water evaporation.
Furthermore, as the water vapor particles continue to move, they will strike, so that some of the water vapor particles are present which pound fluid and return to water. When there is some water vapor that turns into water (condenses), then the water leaves an empty space which will then be filled by other water particles that turn into water vapor (evaporate). And so on, so that water-vapor equilibrium will form, and this condition is called the saturated vapor equilibrium condition.
Well, the pressure caused by this saturated vapor is called the saturated vapor pressure. (note, the gas pressure is caused by the collision between the gas particles and the wall of the container).
The more steam produced by a substance, the more gas particles are generated, the greater the vapor pressure. Some substances have a greater vapor pressure than others. Substances such as ethanol, gasoline, diethyl ether, and others, have a greater vapor pressure than other substances such as water. However, the vapor pressure is not only related to the liquid, the solid also has a vapor pressure, but its value is very small, even negligible.
Substances that are volatile or have a large vapor pressure are called volatile substances. These substances have large vapor pressures because they have a low interparticle attraction so that the interaction between the particles is more easily broken. The opposite of volatile substances is nonvolatile (non-volatile) substances. Such substances are substances that are at room temperature of solid form such as, sugar, salt, urea, glucose, etc.
Vapor pressure is affected by temperature. The bigger the temperature, the kinetic energy of the substance gets bigger so that the interaction between the particles is weakened which consequently becomes easier to break, so it will be faster as the vapor (gas). That is, the vapor pressure increases.
Well, from the description above, we can conclude that the vapor pressure of a substance can also be defined as the amount of pressure or ability of the particles of the substance to break away from the group and exit freely as gas (yawn).
So a brief explanation of the vapor pressure, I am 
