Basically means that an incompressible fluid transmits pressure.  A good example which you can think about is squeezing a toothpaste tube at one end and getting the paste at the other end.

Pascals law states that the increase in pressure at one point of the enclosed liquid in equilibrium of rest is transmitted equally to all other points of the liquid and also to the walls of the container, provided the effect of gravity is neglected.

To understand better with example  - the increase in pressure at one point – squeezing the tube

• of the enclosed liquid in equilibrium of rest – Tooth paste inside the tube
• is transmitted equally to all other points of the liquid and also to the walls of the container – Tooth paste coming out at other end with change in shape of the tooth paste tube

Mathematically, Pressure P = F/A

The principle was first stated clearly in 1652 by Blaise Pascal and the unit of pressure is named after this scientist.