Pressure is the amount of force exerted by area applied in a direction perpendicular to the surface of the object.$^1$ The S.I unit of pressure is measured in Pascals(Pa).$^1$
Pressure relates the amount of force applied to the area in which it is applied.$^1$
The formula for pressure is $P =\frac{F}{A}$
A fluid is a liquid or a gas. In general, a fluid is anything that has the property of fluidity.$^0$ Fluidity is a continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container.$^3$
Fluid pressure is the pressure exerted by a fluid at a given point of space due to its weight and motion.$^2$
When the object is submerged into the fluid, it pushes the molecules of the fluid out of the way. However gravity forces the molecules to the lowest level possible. Hence, the pressure acts on all sides. That is because pressure itself is scalar. It has no direction. However it is drawn with arrows. These arrows indicate the direction of the force that is acting on the object.$^2$
In order to frame the formula for fluid pressure, we can use the general formula for pressure.
$$ P = \frac{F}A\newline P = \frac{mg}{A}\newline P = \frac{(\rho Ah)g}{A}\newline P = \rho gh $$
Where $P$ is the fluid pressure, $\rho$ is the fluid density, $g$ is gravity, $h$ is the depth of the object below the water.
In this derivation, the force is taken as the weight of the fluid which is equal to mass into gravity. Mass is equal to density into volume. Volume is equal to area into height. The area component cancel out.$^2$
Atmospheric pressure is the amount of pressure exerted by the weight of the atmosphere on Earth’s surface.$^2$ It would follow, then, that the atmospheric pressure reduces with increasing altitude as the density reduces. However, at nearly all measurements at the surface of Earth the atmospheric pressure is the same, $1.01×10^5 \text{ Pa}$. This is also referred to as 1 atm.$^2$